Carbon powder containing lithium iron phosphate cathode material

Abstract

Providing high-performance cathode materials manufactured from low-cost starting materials. [Solution] Aggregated particles comprising a porous carbon matrix and a plurality of cathode material particles at least partially embedded within the matrix, and a method for producing them using mainly aqueous chemistry.

Description

[Technical Field]

[0001] Cross-reference of related applications This application is a U.S. Provisional Patent Application No. 63 / 381777 filed on November 1, 2022, U.S. Provisional Patent Application No. 63 / 381771 filed on November 1, 2022, U.S. Provisional Patent Application No. 63 / 381694 filed on October 31, 2022, U.S. Provisional Patent Application No. 63 / 381687 filed on October 31, 2022, U.S. Provisional Patent Application No. 63 / 381681 filed on October 31, 2022, U.S. Provisional Patent Application No. 63 / 381672 filed on October 31, 2022, and U.S. Provisional Patent Application No. 63 / 381672 filed on October 31, 2022. We claim priority and interest in Provisional Patent Application No. 63 / 381666, U.S. Provisional Patent Application No. 63 / 416996 filed on 18 October 2022, U.S. Provisional Patent Application No. 63 / 378756 filed on 7 October 2022, U.S. Provisional Patent Application No. 63 / 352571 filed on 15 June 2022, U.S. Provisional Patent Application No. 63 / 336640 filed on 29 April 2022, and U.S. Provisional Patent Application No. 63 / 326353 filed on 1 April 2022, each of which is incorporated herein by reference in whole.

[0002] This disclosure relates to improved cathode materials for lithium-ion batteries. In particular, this disclosure relates to porous carbon matrix materials including a cathode material-doped carbon aerogel, and methods for producing the same. [Background technology]

[0003] One of the most common types of rechargeable batteries is the lithium-ion battery (LIB). LIBs are widely used in a variety of applications, from portable electronic devices 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 has been made of graphite and / or alloy materials (e.g., Si), or oxides (e.g., Li4Ti5O). 12) is formed in a graphite layer, and lithium ions are inserted into the graphite layer during the charging cycle, where energy storage takes place. LIB cathode materials are generally oxide compounds of nickel, cobalt, or manganese ("NCM") or aluminum. NCM cathode materials are interesting because they have a high charging capacity (approximately 200 milliampere-hours / gram (mAh / g)) compared to other types of cathode materials. However, these materials can be expensive to prepare and may have adverse environmental impacts as they require obtaining and processing expensive ores to provide the necessary precursors, generating toxic waste in the process.

[0004] Recently, LFP (LiFePO4) has emerged as one of the most promising cathode materials for lithium-ion batteries (LIBs), eliminating conflict metals such as nickel and cobalt, which are widely used in non-LFP LIBs (e.g., NMC chemicals). However, the main challenge with this material lies in its cost / performance in large-scale production, particularly the cost of raw materials and manufacturing processes. LFP materials that function well in batteries (i.e., approaching a theoretical capacity of 170 milliampere-hours / gram (mA / g) and minimizing capacity loss over at least 500 or 1000 charge cycles) can be manufactured from various precursors using various technologies. However, these technologies may generate wastewater, requiring expensive and energy-intensive processing technologies.

[0005] On the other hand, low-cost (and low-quality) LFPs (here referred to as "LC-LFP") can be economically manufactured from iron oxide (mineral), but their performance is inferior. The inferior performance of some types of LFPs may be due to non-uniform or poor quality carbon coating of the particles (which increases the internal electrical resistance of the material) and / or crystallographic defects that hinder lithium ion mobility. Both electron transfer resistance and ion transfer resistance show a positive correlation with particle size. Therefore, optimizing the performance of LFP electrodes, especially for use in lithium-ion batteries (LIBs), involves reducing the particle size of LFPs to less than 1 micron.

[0006] Optimizing the performance of LFP electrodes may include reducing crystal defects through annealing. However, particle size reduction techniques and high-temperature processing are incompatible because high-temperature processing leads to undesirable crystal growth in the (desired) small particles of LFP. This undesirable crystal growth creates electronically isolated zones within the cathode particles, making it difficult to access lithium (Li) ions and reducing charging capacity. Therefore, targeting high-performance LFP electrodes suitable for LIB applications requires the implementation of conductive surface coatings using advanced polymer and carbon technologies and particle-level engineering.

[0007] Therefore, this disclosure aims to meet the technical needs for high-performance LFP materials manufactured from low-cost starting materials, while overcoming the aforementioned drawbacks of conventional materials and methods. [Overview of the Initiative]

[0008] This technology generally relates to aggregate particles containing porous carbon matrix particles and multiple cathode material particles, as well as methods for preparing cathode materials within a conductive carbon matrix. This method generally involves providing a slurry of cathode material particles in a solution of an organogel precursor material suitable for subsequent gelation to form an organogel (e.g., a polyimide or polyamic acid gel), gelling the organogel precursor material to form an organic matrix in the form of a wet organogel, and drying the wet organogel. Subsequently, the dried organogel (aerogel, xerogel, or aerogel-like) is thermally decomposed to form a porous carbon matrix material doped with cathode material particles.

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

[0010] LFP alone has low conductivity, and it is known in the art that additional carbon (i.e., LFP / C) is provided to obtain the required conductivity. Previously reported methods provide, for example, LFP cathode materials containing carbon, which is usually added using carbon particles (e.g., carbon black) or by thermal decomposition of a mixture of LFP precursors and sugar molecules. None of these conventional methods for introducing carbon into cathode materials provide a conductive matrix equivalent to that provided according to the methods disclosed herein.

[0011] The disclosed products and methods can use LFP from any source, including low-cost / low-quality LFP (LC-LFP) materials, as starting materials, making the disclosed products and methods cost-effective. Furthermore, the products and methods disclosed herein overcome the inferior performance of such materials by providing a porous carbon matrix in which LFP particles are at least partially embedded, thereby providing the carbon necessary for improved conductivity. The amount of carbon present in the final material can be adjusted to the minimum amount required for conductivity, thereby maximizing the amount of LFP, which is the charge-storing component in the final battery.

[0012] The disclosed formation of the carbon matrix by thermal decomposition is carried out herein at a temperature high enough to pyrolyze the polymer of the organogel (e.g., polyamic acid, polyimide, or a combination thereof) into carbon, while simultaneously preventing undesirable crystal growth in the LFP particles. Without wishing to be bound by theory, it is believed that by at least partially embedding the LFP particles within the pores of the carbon matrix particles, the possibility of this crystal growth is prevented, or else the charge capacity of the battery cell will decrease.

[0013] Furthermore, the methods disclosed herein generally utilize environmentally friendly chemistry, and when a non-aqueous solvent is used, the solvent can be recycled, resulting in an overall lower environmental impact of the method.

[0014] In one aspect, agglomerated particles are provided that include matrix particles comprising porous carbon and a plurality of cathode material particles at least partially embedded within the matrix particles.

[0015] In some aspects, the plurality of cathode material particles include lithium metal phosphate (LMP) particles.

[0016] In some aspects, the metal (M) of the LMP is selected from the group consisting of Fe, Mn, V, and combinations of Fe and Mn.

[0017] In some aspects, the matrix particles have a particle size of 100 nm to 20 microns, or 1 to 10 microns.

[0018] In some aspects, at least some of the plurality of cathode material particles have an average particle size D50 of less than 250 nm, or less than 150 nm.

[0019] In some aspects, the internal specific surface area of the matrix particles corresponding to the internal pores is 50 m 2 / gram to 150 m 2 / gram.

[0020] In some embodiments, at least a portion of the internal specific surface area is configured to be accessible to the electrolyte.

[0021] In some embodiments, the matrix particles include an aerogel or a xerogel.

[0022] In some embodiments, the xerogel or aerogel is formed as one or more beads, or as a monolith.

[0023] In some embodiments, the aerogel or xerogel is derived from an organogel comprising a polyimide, a polyamic acid, or a combination thereof.

[0024] In some embodiments, the aerogel or xerogel is a carbonized organogel.

[0025] In some embodiments, the matrix particles have a pore structure including a fibril form.

[0026] In some embodiments, the fibril form includes struts of a carbonized material having a width in the range of about 2 to about 10 nm.

[0027] In some embodiments, the matrix particles have a substantially uniform pore size distribution.

[0028] In some embodiments, the matrix particles have an average pore size of about 1 to about 50 nm, or about 5 to about 25 nm.

[0029] In some embodiments, the matrix particles include pores, and at least a portion of the pores are configured to accommodate cathode material particles.

[0030] In some embodiments, the weight ratio of carbon in the matrix material to the cathode material is less than 30:70, less than 10:90, or less than 5:95.

[0031] In another embodiment, a method is provided for preparing aggregate particles comprising porous carbon matrix particles and a plurality of cathode material particles at least partially embedded within the matrix particles, the method being: (a) Prepare an aqueous solution of a polyamic acid salt, (b) Mixing cathode material particles with an aqueous solution of a polyamic acid salt, (c1) Gelating the mixture from step (b) to form an organogel containing dispersed cathode material particles, drying the organogel from step (c1) to form a dried intermediate, or (c2) Drying the mixture from step (b) to form a dried intermediate, (d) Carbonizing the dried intermediate to form aggregate particles.

[0032] In some embodiments, preparing an aqueous solution of a polyamic acid salt is Mixing a water-soluble diamine, a water-soluble carbonate or bicarbonate, and a tetracarboxylic dianhydride in water, This includes reacting components to obtain a solution of a polyamic acid salt.

[0033] In some embodiments, the mixture is Dissolving a water-soluble diamine in water to form an aqueous diamine solution, Adding a water-soluble carbonate or bicarbonate to an aqueous diamine solution, Adding tetracarboxylic dianhydride to an aqueous solution of a diamine and a water-soluble carbonate or bicarbonate to form a solution, This includes stirring the solution at a temperature in the range of approximately 4 to 60°C for a period of approximately 1 hour to 4 days.

[0034] In some embodiments, the mixture is Dissolving a water-soluble diamine in water to form an aqueous diamine solution, Adding tetracarboxylic dianhydride to an aqueous diamine solution to form a suspension, The suspension is stirred at a temperature ranging from approximately 4 to 60°C for a period ranging from approximately 1 hour to approximately 4 days. Adding a water-soluble carbonate or bicarbonate to the suspension, The method includes stirring the suspension at a temperature in the range of approximately 4 to 60°C for a period of approximately 1 hour to 4 days to obtain an aqueous solution of the polyamic acid salt.

[0035] In some embodiments, the mixture is The simultaneous or rapid and continuous addition of a water-soluble diamine, tetracarboxylic dianhydride, and a water-soluble carbonate or bicarbonate to water, The method involves stirring the resulting mixture at a temperature in the range of approximately 4 to approximately 60°C for a period of approximately 1 hour to approximately 4 days to obtain an aqueous solution of polyamic acid salt.

[0036] In some embodiments, the water-soluble carbonate or bicarbonate comprises lithium, sodium, potassium, ammonium, or guanidinium cations. In some embodiments, the water-soluble carbonate or bicarbonate is selected from the group consisting of lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, ammonium bicarbonate, guanidinium carbonate, and combinations thereof.

[0037] In some embodiments, the water-soluble carbonate or bicarbonate is a carbonate, and the molar ratio of the water-soluble carbonate to the diamine is approximately 1 to approximately 1.4, or the water-soluble carbonate or bicarbonate is a bicarbonate, and the molar ratio of the water-soluble bicarbonate to the diamine is approximately 2 to approximately 2.8.

[0038] In some embodiments, the molar ratio of tetracarboxylic dianhydride to diamine is approximately 0.9 to approximately 1.1.

[0039] In some embodiments, the tetracarboxylic dianhydride is selected from the group consisting of biphthalic acid dianhydride (BPDA), benzophenone tetracarboxylic dianhydride (BTDA), oxydiphthalic acid dianhydride (ODPA), naphthalyl tetracarboxylic dianhydride, perylene tetracarboxylic dianhydride, and pyromellitic acid dianhydride (PMDA).

[0040] In some embodiments, the diamine is 1,3-phenylenediamine, 1,4-phenylenediamine, or a combination thereof. In some embodiments, the diamine is 1,4-phenylenediamine.

[0041] In some embodiments, the concentration range of polyamic acid salts in aqueous solution is approximately 0.01 to approximately 0.3 g / cm³ based on the weight of the polyamic acid. 3 That is the case.

[0042] In some embodiments, drying the organogel or intermediate is Optionally, the organogel or intermediate may be washed or the solvent changed. This includes exposing an organogel or intermediate to high-temperature conditions to freeze-dry the organogel or intermediate, or contacting the organogel or intermediate with supercritical fluid carbon dioxide.

[0043] In some embodiments, the porous carbon matrix comprises an aerogel or xerogel.

[0044] In some embodiments, carbonization is carried out in an inert atmosphere at a temperature of at least about 650°C.

[0045] In some embodiments, the cathode material particles comprise at least one lithium metallic phosphate (LMP), where the metal (M) is selected from iron, manganese, vanadium, and a combination of iron and manganese.

[0046] In some embodiments, the cathode material particles contain LiFePO4 or consist of LiFePO4 in nature.

[0047] In some embodiments, the cathode material is ground before or during step (b).

[0048] In some embodiments, grinding includes grinding using a roller mill, planetary ball mill, or bead agitation mill, and optionally using at least one grinding medium selected from alumina, zirconia, and stainless steel.

[0049] In some embodiments, grinding includes dispersing the cathode material in a liquid phase optionally selected from water, ethanol, isopropanol, ethylene glycol, acetone, or a mixture thereof, and wet grinding the cathode material.

[0050] In some embodiments, the grinding includes dispersing the cathode material in an aqueous solution of a polyamic acid salt and wet grinding the cathode material during step (b) to obtain cathode material particles.

[0051] In some embodiments, step (b) includes mixing the cathode material for a period of time and under conditions sufficient to disperse it in an aqueous solution.

[0052] In some embodiments, the organogel comprises a polyimide, and the gelation in step (c1) comprises adding a gelation initiator to convert the polyamic acid to a polyimide. In some embodiments, the gelation initiator is acetic anhydride.

[0053] In some embodiments, the gelation of the mixture in step (c1) is carried out in a mold to form a wet gel monolith.

[0054] In some embodiments, the method further includes crushing the wet gel monolith into multiple fragments before drying.

[0055] In some embodiments, this method further includes (e) grinding the dried material of step (c1).

[0056] In some embodiments, grinding produces particles having an average particle size D50 of less than approximately 50 microns.

[0057] In some embodiments, step (c1) further includes adding a gelling initiator and then mixing an aqueous solution of a polyamic acid salt with a non-aqueous miscible liquid to form an emulsion.

[0058] In some embodiments, the gelation initiator is acetic anhydride.

[0059] In some embodiments, the mixing to form an emulsion is carried out for about 1 to about 30 minutes, or about 4 to about 15 minutes.

[0060] In some embodiments, the organogel comprises a polyamic acid, and the gelation in step (c1) comprises adding a gelation initiator to convert the salt of the polyamic acid into a polyamic acid organogel, the gelation initiator being an acid. In some embodiments, the acid is a carboxylic acid. In some embodiments, the carboxylic acid is acetic acid.

[0061] In some embodiments, the method further includes, between steps (b) and (c1), mixing the mixture from step (b) with a non-aqueous miscible liquid to form an emulsion.

[0062] In some embodiments, the mixing is carried out for a maximum of approximately 10 minutes, or for approximately 1 to 3 minutes.

[0063] In some embodiments, mixing is carried out using a homogenizer. In some embodiments, the homogenizer is operated at a speed of at least 1000 rpm, for example, about 1000 to about 9000 rpm.

[0064] In some embodiments, the non-aqueous miscible liquid is selected from the group consisting of mineral spirits, hexane, heptane, kerosene, octane, toluene, other hydrocarbons, and combinations thereof. In some embodiments, the non-aqueous miscible liquid is a mineral spirit.

[0065] In some embodiments, the non-aqueous miscible liquid further comprises a surfactant dissolved therein. In some embodiments, the surfactant is present in a concentration of about 1-2% by weight relative to the non-aqueous miscible liquid.

[0066] In some embodiments, the method further includes separating the organogel beads formed in step (c1) before drying. In some embodiments, the separation includes decanting the non-aqueous miscible liquid and optionally recycling the non-aqueous miscible liquid.

[0067] In some embodiments, the beads have an average size ranging from approximately 5 to approximately 30 microns.

[0068] In some embodiments, this method further includes washing the gel beads with water, C1-C4 alcohols, acetone, acetonitrile, ether, tetrahydrofuran, toluene, liquid carbon dioxide, or a combination thereof.

[0069] In some embodiments, at least a portion of the multiple cathode material particles have an average particle size D50 of less than 250 nm or less than 150 nm.

[0070] In some embodiments, the drying step (c2) is spray drying.

[0071] In yet another embodiment, aggregate particles are provided, which are obtained by or can be obtained by a method disclosed herein, comprising porous carbon matrix particles and a plurality of cathode material particles at least partially embedded within the matrix particles.

[0072] In some embodiments, the weight ratio of carbon in the matrix material to the cathode material is less than 30:70, less than 10:90, or less than 5:95.

[0073] In yet another embodiment, an electrode comprising aggregated particles disclosed herein is provided.

[0074] In yet another embodiment, an energy storage device comprising aggregated particles disclosed herein is provided. In some embodiments, the energy storage device is a lithium-ion battery.

[0075] This disclosure includes, but is not limited to, the following aspects:

[0076] Embodiment 1: Agglomerated particles comprising matrix particles containing porous carbon and a plurality of cathode material particles at least partially embedded within the matrix particles.

[0077] Embodiment 2: The aggregated particle according to Embodiment 1, wherein the plurality of cathode material particles include lithium metal phosphate (LMP) particles.

[0078] Embodiment 3: The aggregated particle according to Embodiment 1 or 2, wherein the metal (M) of the LMP is selected from the group consisting of Fe, Mn, V, and combinations of Fe and Mn.

[0079] Embodiment 4: The aggregated particles according to any one of Embodiments 1 to 3, wherein the matrix particles have a particle size of 100 nm to 20 microns, or 1 to 10 microns.

[0080] Embodiment 5: The aggregated particle according to any one of Embodiments 1 to 4, wherein at least a portion of the plurality of cathode material particles have an average particle size D50 of less than 250 nm.

[0081] Embodiment 6: The aggregated particle according to any one of Embodiments 1 to 5, wherein at least a portion of the plurality of cathode material particles have an average particle size D50 of less than 150 nm.

[0082] Embodiment 7: The matrix particles have an internal specific surface area corresponding to the internal pores of 50 m². 2 / gram ~ 150ml 2 aggregated particles according to any one of embodiments 1 to 6, which are / grams.

[0083] Embodiment 8: The aggregated particle according to any one of Embodiments 1 to 7, wherein at least a portion of the internal specific surface area is configured to allow access for the electrolyte.

[0084] Embodiment 9: The aggregated particle according to any one of Embodiments 1 to 8, wherein the matrix particle comprises an aerogel or a xerogel.

[0085] Embodiment 10: The aggregated particles according to Embodiment 9, wherein the aerogel of the xerogel is formed as one or more beads or monoliths.

[0086] Embodiment 11: The aggregated particles according to any one of Embodiments 9 to 10, wherein the aerogel or xerogel is derived from an organogel containing a polyimide, a polyamic acid, or a combination thereof.

[0087] Embodiment 12: The aggregated particles according to any one of Embodiments 9 to 11, wherein the aerogel or xerogel is a carbonized organogel.

[0088] Embodiment 13: The aggregated particle according to any one of Embodiments 1 to 12, wherein the matrix particle has a pore structure including a fibril morphology.

[0089] Embodiment 14: The aggregated particle according to Embodiment 13, wherein the fibril morphology includes a support column of a carbonized material having a width in the range of about 2 to about 10 nm.

[0090] Embodiment 15: The aggregated particle according to any one of Embodiments 1 to 14, wherein the matrix particles have a substantially uniform pore size distribution.

[0091] Embodiment 16: The aggregated particle according to any one of Embodiments 1 to 15, wherein the matrix particles have an average pore diameter of about 1 to about 50 nm, or about 5 to about 25 nm.

[0092] Embodiment 17: The aggregated particle according to any one of embodiments 1 to 16, wherein the matrix particles include pores, and at least a portion of the pores are configured to accommodate the cathode material particles.

[0093] Embodiment 18: The aggregated particle according to any one of Embodiments 1 to 17, wherein the weight ratio of carbon in the matrix material to the cathode material is less than 30:70, less than 10:90, or less than 5:95.

[0094] Embodiment 19: A method for preparing aggregated particles comprising porous carbon matrix particles and a plurality of cathode material particles at least partially embedded within the matrix particles, (a) Prepare an aqueous solution of a polyamic acid salt, (b) Mixing cathode material particles with an aqueous solution of the polyamic acid salt, (c1) Gelating the mixture from step (b) to form an organogel containing dispersed cathode material particles, and drying the organogel from step (c1) to form a dried intermediate, or (c2) Dry the mixture from step (b) to form a dried intermediate, (d) The method comprising carbonizing the dried intermediate to form the aggregate particles.

[0095] Embodiment 20: The preparation of an aqueous solution of the polyamic acid salt is Mixing a water-soluble diamine, a water-soluble carbonate or bicarbonate, and a tetracarboxylic dianhydride in water, The method according to embodiment 19, comprising reacting the components to obtain a solution of the salt of the polyamic acid.

[0096] Embodiment 21: The mixture is Dissolving a water-soluble diamine in water to form an aqueous diamine solution, Adding the aforementioned water-soluble carbonate or bicarbonate to the diamine aqueous solution, Adding tetracarboxylic dianhydride to the aqueous solution of the diamine and the water-soluble carbonate or bicarbonate to form a solution, The method according to embodiment 20, comprising stirring the solution at a temperature in the range of about 4 to about 60°C for a period of about 1 hour to about 4 days.

[0097] Embodiment 22: The mixture is Dissolving a water-soluble diamine in water to form an aqueous diamine solution, Adding tetracarboxylic dianhydride to the aqueous solution of the diamine to form a suspension, The suspension is stirred at a temperature in the range of approximately 4 to approximately 60°C for a period of approximately 1 hour to approximately 4 days. Adding the aforementioned water-soluble carbonate or bicarbonate to the suspension, The method according to embodiment 20, comprising stirring the suspension at a temperature in the range of about 4 to about 60°C for a period of about 1 hour to about 4 days to obtain an aqueous solution of the polyamic acid salt.

[0098] Embodiment 23: The mixture is The simultaneous or rapid and continuous addition of a water-soluble diamine, tetracarboxylic dianhydride, and a water-soluble carbonate or bicarbonate to water, The method according to embodiment 20, comprising stirring the obtained mixture at a temperature in the range of about 4 to about 60°C for a period of about 1 hour to about 4 days to obtain an aqueous solution of the polyamic acid salt.

[0099] Embodiment 24: The method according to any one of Embodiments 19 to 23, wherein the water-soluble carbonate or bicarbonate comprises lithium, sodium, potassium, ammonium, or guanidinium cation.

[0100] Embodiment 25: The method according to any one of Embodiments 19 to 24, wherein the water-soluble carbonate or bicarbonate is selected from the group consisting of lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, ammonium bicarbonate, guanidinium carbonate, and combinations thereof.

[0101] Embodiment 26: The method according to any one of Embodiments 19 to 25, wherein the water-soluble carbonate or bicarbonate is a carbonate, and the molar ratio of the water-soluble carbonate to the diamine is about 1 to about 1.4, or the water-soluble carbonate or bicarbonate is a bicarbonate, and the molar ratio of the water-soluble bicarbonate to the diamine is about 2 to about 2.8.

[0102] Embodiment 27: The method according to any one of Embodiments 19 to 26, wherein the molar ratio of the tetracarboxylic dianhydride to the diamine is about 0.9 to about 1.1.

[0103] Embodiment 28: The method according to any one of Embodiments 19 to 27, wherein the tetracarboxylic dianhydride is selected from the group consisting of biphthalic acid dianhydride (BPDA), benzophenone tetracarboxylic dianhydride (BTDA), oxydiphthalic acid dianhydride (ODPA), naphthalyl tetracarboxylic dianhydride, perylene tetracarboxylic dianhydride, and pyromellitic acid dianhydride (PMDA).

[0104] Embodiment 29: The method according to any one of Embodiments 19 to 28, wherein the diamine is 1,3-phenylenediamine, 1,4-phenylenediamine, or a combination thereof.

[0105] Embodiment 30: The method according to any one of Embodiments 19 to 29, wherein the diamine is 1,4-phenylenediamine.

[0106] Embodiment 31: The concentration range of the polyamic acid salt in the aqueous solution is approximately 0.01 to approximately 0.3 g / cm³ based on the weight of the polyamic acid. 3 The method according to any one of embodiments 19 to 30.

[0107] Embodiment 32: Drying the organogel or intermediate is Optionally, the organogel or intermediate may be washed or the solvent may be changed. The method according to any one of embodiments 19 to 31, comprising exposing the organogel or intermediate to high-temperature conditions to freeze-dry the organogel or intermediate, or contacting the organogel or intermediate with supercritical fluid carbon dioxide.

[0108] Embodiment 33: The method according to any one of Embodiments 19 to 32, wherein the porous carbon matrix comprises an aerogel or a xerogel.

[0109] Embodiment 34: The method according to any one of Embodiments 19 to 33, wherein the carbonization is carried out in an inert atmosphere at a temperature of at least about 650°C.

[0110] Embodiment 35: The method according to any one of Embodiments 19 to 34, wherein the cathode material particles comprise at least one lithium metallic phosphate (LMP), and the metal (M) is selected from iron, manganese, vanadium, and a combination of iron and manganese.

[0111] Embodiment 36: The method according to any one of Embodiments 19 to 35, wherein the cathode material particles contain LiFePO4 or consist essentially of LiFePO4.

[0112] Embodiment 37: The method according to any one of Embodiments 19 to 36, wherein the cathode material is pulverized before or during step (b).

[0113] Embodiment 38: The method according to Embodiment 37, wherein the grinding comprises grinding using a roller mill, planetary ball mill or bead agitator mill, and optionally using at least one grinding medium selected from alumina, zirconia, and stainless steel.

[0114] Embodiment 39: The method according to Embodiment 37 or 38, wherein the grinding comprises dispersing the cathode material in a liquid phase optionally selected from water, ethanol, isopropanol, ethylene glycol, acetone, or a mixture thereof, and wet grinding the cathode material.

[0115] Embodiment 40: The method according to any one of Embodiments 37 to 39, wherein the grinding comprises dispersing the cathode material in an aqueous solution of the salt of the polyamic acid and wet grinding the cathode material during step (b) to obtain cathode material particles.

[0116] Embodiment 41: The method according to any one of Embodiments 19 to 40, wherein step (b) comprises mixing for a period of time and under conditions sufficient to disperse the cathode material in the aqueous solution.

[0117] Embodiment 42: The method according to any one of Embodiments 19 to 41, wherein the organogel contains polyimide, and the gelation in step (c1) comprises adding a gelation initiator to convert the polyamic acid to the polyimide.

[0118] Embodiment 43: The method according to Embodiment 42, wherein the gelling initiator is acetic anhydride.

[0119] Embodiment 44: The method according to any one of Embodiments 19 to 43, wherein the gelation of the mixture in step (c1) is carried out in a mold to form a wet gel monolith.

[0120] Embodiment 45: The method according to Embodiment 44, further comprising crushing the wet gel monolith into a plurality of fragments before drying.

[0121] Embodiment 46: The method according to any one of Embodiments 19 to 45, further comprising grinding the dried material of step (c1).

[0122] Embodiment 47: The method according to Embodiment 46, wherein the grinding produces particles having an average particle size D50 of less than approximately 50 microns.

[0123] Embodiment 48: The method according to any one of Embodiments 19 to 43, wherein step (c1) further comprises adding the gelling initiator and then mixing an aqueous solution of the polyamic acid salt with a non-aqueous miscible liquid to form an emulsion.

[0124] Embodiment 49: The method according to Embodiment 48, wherein the gelling initiator is acetic anhydride.

[0125] Aspect 50: The method according to any one of Aspects 48 to 49, wherein the mixing for forming an emulsion is carried out for about 1 to about 30 minutes, or for about 4 to about 15 minutes.

[0126] Embodiment 51: The method according to any one of Embodiments 19 to 41, wherein the organogel contains a polyamic acid, and the gelation in step (c1) comprises adding a gelation initiator to convert a salt of the polyamic acid into a polyamic acid organogel, wherein the gelation initiator is an acid.

[0127] Embodiment 52: The method according to Embodiment 51, wherein the acid is a carboxylic acid.

[0128] Embodiment 53: The method according to Embodiment 52, wherein the carboxylic acid is acetic acid.

[0129] Embodiment 54: The method according to any one of embodiments 51 to 53, further comprising mixing the mixture of step (b) with a non-aqueous miscible liquid to form an emulsion between steps (b) and (c1).

[0130] Embodiment 55: The method according to Embodiment 54, wherein the mixing is performed for a maximum of about 10 minutes, or for about 1 to about 3 minutes.

[0131] Embodiment 56: The method according to Embodiment 54 or 55, wherein the mixing is carried out using a homogenizer.

[0132] Embodiment 57: The method according to Embodiment 56, wherein the homogenizer is operated at a speed of at least 1000 rpm, for example, about 1000 to about 9000 rpm.

[0133] Embodiment 58: The method according to any one of Embodiments 48-50 or 54-57, wherein the non-aqueous miscible liquid is selected from the group consisting of mineral spirits, hexane, heptane, kerosene, octane, toluene, other hydrocarbons, and combinations thereof.

[0134] Embodiment 59: The method according to Embodiment 58, wherein the non-aqueous miscible liquid is a mineral spirit.

[0135] Embodiment 60: The method according to any one of Embodiments 48-50 or 54-59, wherein the non-aqueous miscible liquid further comprises a surfactant dissolved therein.

[0136] Embodiment 61: The method according to Embodiment 60, wherein the surfactant is present in a concentration of about 1 to 2% by weight relative to the non-aqueous miscible liquid.

[0137] Embodiment 62: The method according to any one of embodiments 48 to 61, further comprising separating the beads of the organogel formed in step (c1) before drying.

[0138] Embodiment 63: The method according to Embodiment 62, wherein the separation comprises decanting the non-aqueous miscible liquid and optionally recycling the non-aqueous miscible liquid.

[0139] Embodiment 64: The method according to Embodiment 62 or 63, wherein the beads have an average size in the range of about 5 to about 30 microns.

[0140] Embodiment 65: The method according to any one of embodiments 62 to 64, further comprising washing the gel beads with water, C1-C4 alcohols, acetone, acetonitrile, ether, tetrahydrofuran, toluene, liquid carbon dioxide, or a combination thereof.

[0141] Embodiment 66: The method according to any one of embodiments 19 to 65, wherein at least a portion of the plurality of cathode material particles have an average particle size D50 of less than 250 nm or less than 150 nm.

[0142] Embodiment 67: The method according to any one of Embodiments 19 to 66, wherein the drying step (c2) is spray drying.

[0143] Embodiment 68: Aggregated particles comprising porous carbon matrix particles and a plurality of cathode material particles at least partially embedded within the matrix particles, which can be obtained by or by the method described in any one of Embodiments 19 to 67.

[0144] Embodiment 69: The aggregated particle according to Embodiment 68, wherein the weight ratio of carbon in the matrix material to the cathode material is less than 30:70, less than 10:90, or less than 5:95.

[0145] Embodiment 70: An electrode containing aggregated particles as described in any one of Embodiments 1 to 18 or 68 to 69.

[0146] Embodiment 70: An energy storage device containing aggregated particles according to any one of Embodiments 1 to 18 or 68 to 69.

[0147] Embodiment 71: The energy storage device according to Embodiment 70, wherein it is a lithium-ion battery.

[0148] To provide an understanding of the aspects of this technology, please refer to the accompanying drawings, which are not necessarily drawn to scale. These aspects are shown as examples, not as an extension, of the accompanying drawings. Please note that references to “an” or “one” aspects in this disclosure do not necessarily refer to the same aspects, but rather mean at least one. [Brief explanation of the drawing]

[0149] [Figure 1] Figure 1 is a schematic diagram illustrating a method 100 for producing aggregated particles according to one or more non-limiting embodiments of the present disclosure. [Figure 2] Figure 2 is a schematic diagram illustrating a further method 200 for producing aggregated particles according to one or more non-limiting embodiments of the present disclosure. [Figure 3] Figure 3 is a schematic diagram illustrating yet another method 300 for producing aggregated particles according to one or more non-limiting embodiments of the present disclosure. [Figure 4] Figure 4 is a schematic diagram illustrating another method 400 for producing aggregated particles according to one or more non-limiting embodiments of the present disclosure. [Figure 5A] Figure 5A is a schematic diagram of aggregated particles according to one or more non-limiting embodiments of the present disclosure. [Figure 5B] Figure 5B is a schematic diagram of aggregated particles according to one or more non-limiting embodiments of the present disclosure. [Figure 6] Figure 6 is a schematic diagram of aggregated particles 600 according to one or more non-limiting embodiments of the present disclosure. [Figure 7] Figure 7 is a schematic diagram of aggregated particles according to one or more non-limiting embodiments of the present disclosure. [Figure 8A] Figure 8A is a scanning electron microscope image of aggregated particles according to one or more non-limiting embodiments of the present disclosure. [Figure 8B] Figure 8B is a scanning electron microscope image of aggregated particles according to one or more non-limiting embodiments of the present disclosure. [Figure 8C] Figure 8C is a scanning electron microscope image of aggregated particles according to one or more non-limiting embodiments of the present disclosure. [Figure 8D] Figure 8D is a scanning electron microscope image of aggregated particles according to one or more non-limiting embodiments of the present disclosure. [Figure 9] Figure 9 shows the charge-discharge voltage profile of a first cycle including aggregated particles according to one or more non-limiting embodiments of the present disclosure. [Figure 10] Figure 10 is a chart showing rate performance including aggregated particles according to one or more non-limiting aspects of the present disclosure. [Figure 11] Figure 11 is a chart showing the capacity loss including aggregated particles according to one or more non-limiting aspects of the present disclosure. [Modes for carrying out the invention]

[0150] The following description includes numerous specific details for illustrative purposes to provide a complete understanding. One or more embodiments may be implemented without these specific details. Features described in one embodiment can be combined with features described in another embodiment. In some examples, well-known structures and devices are described with reference to block diagrams to avoid unnecessarily complicating the invention.

[0151] I. Overview This disclosure describes LMP-carbon composite materials in which nanoscale LMP particles are at least partially embedded within porous carbon particles or beads having an average particle size of 0.5 to 20 microns. In this specification, “LMP” means “metallic lithium phosphate,” including LFP (“lithium iron phosphate,” where “M” is iron), LMFP (“manganese iron phosphate,” where “M” is a solid solution of manganese and iron), and LVP (“vanadium vanadium phosphate,” where “M” is vanadium), as described herein, and mixtures thereof. In this aggregated particle configuration, the LMP particles are physically separated from each other by being embedded in a carbon matrix, thereby enabling kinetically advantageous access of the electrolyte to the LMP and supporting high charge and discharge rates without significant loss of capacity.

[0152] In principle, LMP obtained through any synthesis method can be pulverized and used in the manufacture of the disclosed LMP-doped carbon aerogel or xerogel composite material. However, for the optimization of cost and scalability, LMP may be manufactured through the lowest cost implementation, in one example being the synthesis of LFP from iron oxide (hematite), phosphate, lithium carbonate, and a carbon source by solid carbon thermal reduction. Such as-manufactured low-cost (and low-quality) LFP (hereinafter referred to as "LC-LFP") has a particle size of ultramicrons and performs very poorly when used as a cathode in a half-cell (e.g., about 20 mAh / g compared to a theoretical specific capacity of 169.9 mAh / g). Pulverizing the aforementioned LC-LFP can increase the capacity to about 80 mAh / g, but this is still less than half of the theoretical capacity. For example, pulverizing the same LFP for several hours increases the capacity to 78 mAh / g, which is significantly higher than the as-manufactured LC-LFP, demonstrating the suppressive effect of large particle size on cathode capacity. Despite the fourfold increase, this capacity is still too low for many commercial applications, particularly transportation applications (e.g., electric vehicles).

[0153] According to this disclosure, it has been surprisingly found that the battery performance of LC-LFPs can be significantly improved when they are embedded in a porous carbon matrix such as carbon aerogel or xerogel with various shape factors, including monoliths and microbeads. The disclosed LFP-carbon aerogel composite beads show that the practical capacity of LFPs increases by more than 50% compared to crushed LFPs alone, resulting in capacities exceeding 145 mAh / g, where the same LFPs in pre-carbon aggregate form may have capacities of less than 100 mAh / g, or even less than 70 mAh / g. A second unexpected benefit is that the aggregate particle cathode exhibits high-rate performance (80% capacity retention at 1C compared to C / 20). A third benefit is that the LFP-doped aggregate particle cathode exhibits excellent cycle life, with no capacity loss even after 500 cycles at a charge / discharge rate of 1C in half-cells composed of a metallic lithium anode.

[0154] Overall, the newly developed process for improving the performance of LC-LFP can be summarized by the following key features and advantages: (1) High specific volume LFP-carbon aerogel microcomposite beads are obtained from low-cost LC-LFP materials; (2) Higher rate performance is achieved compared to commercially available LFPs; (3) Excellent capacity retention is achieved even at high rate cycles; (4) The carbon aerogel used in the LFP / carbon aerogel material is cost-effective and its manufacture is environmentally friendly; and (5) A new class of LFP material is being developed for a variety of applications.

[0155] To produce the disclosed aggregate particles, LFP produced from any source, including low-cost or bulk LC-LFP, is mixed with a suitable salt solution of polyamic acid to form a slurry. The advantage of this method is that the viscosity of the polyamic acid solution is sufficient to maintain the LFP particles in suspension, and the LFP particles are well dispersed throughout the gel and the final product formed. The LFP can be pulverized before or after mixing with the aqueous solution to reduce the particle size, and furthermore, the LFP can be processed into various forms such as solid monoliths or microbead composites of LFP particles in a polymer matrix. In the microbead composite variation, microdroplets of the polyamate aqueous solution containing the LFP suspension become the dispersed phase in a two-phase emulsion and are gelled during dispersion with a suitable gelling initiator (e.g., an acid anhydride such as acetic anhydride, an acid such as acetic acid, or an acid precursor such as acetic anhydride). The resulting gel microbeads can be dried to produce LFP-doped polyimide, polyamic acid aerogel, or xerogel beads, and these can be carbonized to produce LFP-doped carbon aerogel or xerogel microbeads.

[0156] The preparation of monolithic LFP-doped carbon aerogel microcomposites is as described above, except that instead of an emulsification step, a wet suspension and a gelling initiator are introduced into a mold to form a monolithic wet organogel. After drying the gel to form an aerogel or xerogel, the aerogel or xerogel can be pulverized into a powder and then thermally decomposed to form aggregate particles containing a carbon matrix. Alternatively, the slurry can be spray-dried instead of gelling to form a powder containing LFP particles and polymer. This can then be thermally decomposed again to form a carbon matrix. The aggregate particles limit the undesirable microcrystalline growth of LFP during the carbonization / thermal decomposition process and provide a high-performance cathode with fast ion and electron transfer rates.

[0157] In the first general method of this disclosure, a slurry of LMP (where M may be Fe, Mn / Fe, or V) and an aqueous solution of polyamic acid salt are brought into contact with a gelling initiator (such as an anhydride), the gelling solution is emulsified with a non-aqueous miscible liquid to obtain polyimide gel beads, which are separated, washed, and dried to form LMP-doped aerogel or xerogel beads. In the alternative emulsification process described herein, the slurry is first emulsified to form liquid beads, which are then gelled using a gelling initiator (such as an acid or anhydride) to form wet gel polyamic acid and / or polyimide beads. These beads are again separated, washed, and dried. Thirdly, the emulsification step can be avoided, and the slurry can be gelled in a mold using a gelling initiator (such as an acid or anhydride) to form a monolithic wet organogel (polyamic acid and / or polyimide). This monolith can be crushed into particles and then dried to form an aerogel or xerogel.

[0158] To prepare the LFP-doped carbon aerogel microcomposite beads described herein, commercially available low-cost (and low-performance) LC-LFPs were ball-milled and incorporated into polyimide or polyamic acid microspheres using an emulsion gelation process. The microspheres were dried to obtain low-cost LFP-doped polyimide or polyamic acid xerogels or aerogels, which were then carbonized / annealed to form LFP-doped carbon aerogels or xerogels.

[0159] One or more aspects described herein and / or enumerated in the claims may not be included in this summary section.

[0160] II. Definition The following definitions are provided for terms used in this disclosure. In this application, unless a different meaning is required in the context of the text in which the term appears, the terms defined below will be used.

[0161] The articles "a" and "an" are used herein to refer to one or more (i.e., at least one) grammatical objects of the article. The term "about" as used throughout this specification is used to describe and explain small variations. For example, the term "about" can refer to ±10% or less, ±5% or less, e.g., ±2% or less, ±1% or less, ±0.5% or less, ±0.2% or less, ±0.1% or less, or ±0.05% or less. All numbers herein, whether explicitly stated or not, are modified by the term "about". Values ​​modified by the term "about" naturally include that specific value. For example, "about 5.0" must include 5.0.

[0162] In the context of this disclosure, in some examples, the term “framework” or “framework structure” refers to a network of nanoscale and / or microstructural elements, such as fibrils, pillars, and / or colloidal particles, that form a solid structure of a gel or aerogel. The structural elements constituting the framework structure have at least one characteristic dimension (e.g., length, width, diameter) of about 100 angstroms or less. In the case of pyrolysis or carbide aerogels, the term “framework” or “framework structure” may refer to an interconnected network of linear fibrils, nanoparticles, cocontinuous networks (e.g., networks that transition between fibril and spherical forms, having aspects of both transitional structures), or combinations thereof. In some examples, linear fibrils, nanoparticles, or other structural elements can be linked together (at nodes in some examples) to form a framework that defines pores.

[0163] As used herein, the terms “aerogel” and “aerogel material” refer to a solid object that includes a framework of interconnected solid structures, regardless of shape or size, having a corresponding network of interconnected pores integrated within that framework, and containing a gas such as air as a dispersed interstitial medium. Thus, regardless of the drying method used, an aerogel is an open, non-fluid colloidal or polymer network that expands throughout its entire volume by gas, formed by removing all the leavening agent (e.g., solvent) from a corresponding wet gel without substantial volume reduction or network compression.

[0164] Generally, aerogels have one or more of the following physical and structural properties: (a) average pore size in the range of approximately 2 nm to approximately 100 nm, (b) porosity of approximately 60% or more, and (c) pore size of approximately 1, approximately 10 or approximately 20 to approximately 100 or approximately 1000 nm. 2Specific surface area per gram. Typically, such properties are measured using nitrogen adsorption porosimetry and / or helium pycnometry. It is understood that the inclusion of reinforcing materials or electrochemically active species, such as silicon or lithium iron phosphate, may reduce the porosity or specific surface area of ​​the resulting aerogel composite. Densification may also reduce the porosity of the resulting aerogel composite.

[0165] Aerogel materials can also be further characterized by additional physical properties, such as (d) a pore volume of about 2.0 mL / g or more, preferably about 3.0 mL / g or more, (e) a density of about 0.50 g / cc or less, preferably about 0.25 g / cc or less, and (f) at least 50% of the total pore volume containing pores having a diameter of 2 to 50 nm; however, these additional properties do not need to be met for characterizing a compound as an aerogel material. Unless otherwise stated, references to “aerogel” herein include any aerogel or other open-cell porous material that can be characterized as an aerogel, xerogel, cryogel, ambigel, microporous material, etc., regardless of the material (e.g., polyimide, polyamic acid, or carbon).

[0166] In some embodiments, gel materials are sometimes specifically referred to as xerogels. As used herein, the term “xerogel” refers to a type of aerogel containing an open, non-fluid colloid or polymer network, formed by removing all leavening agents from a corresponding wet gel without taking any precautions to avoid substantial volume loss or to slow compression. Xerogels typically contain a compact structure. Xerogels undergo considerable volume loss during drying at atmospheric pressure, and their porosity generally falls to about 40% or less.

[0167] As used herein, the terms “carbon aerogel” or “carbon xerogel” refer to porous carbon-based materials. Some non-limiting examples of carbon aerogels and xerogels include carbonized aerogels and xerogels such as carbonized polyimide gels. In the context of aerogels and xerogels, the term “carbonized” refers to an organic gel (e.g., polyimide) that has been thermally decomposed to decompose or convert the organogel composition into at least substantially pure carbon. As used herein, the terms “thermal decomposition” or “thermal decomposition” or “carbonization” refer to the decomposition or conversion of an organic matrix into pure or substantially pure carbon caused by heat.

[0168] Monolithic aerogel materials are distinguished from particulate aerogel materials. The term “particulate aerogel materials” refers to aerogel materials in which the majority (by weight) of the aerogel contained therein is in the form of fine particles, particles, granules, beads, or powder, which can be bound together (i.e., via a binder such as a polymer binder) or compressed together, but do not have interconnected aerogel nanostructures between the individual particles. Collectively, this form of aerogel material is considered to have a powder or particulate form (as opposed to a monolithic form). Note that although the individual particles of powder have a single structure, the individual particles are not considered monoliths in this specification. The incorporation of aerogel powder into an electrochemical cell typically involves the preparation of a paste or slurry from the powder, casting onto a substrate and drying, and optionally including calendering.

[0169] In the context of this disclosure, the terms “binderless” or “binder-free” (or their derivatives) refer to materials that substantially do not contain binders or adhesives for bonding materials together. For example, monolithic nanoporous carbon materials do not contain binders because their framework is formed as a single continuous interconnected structure. Advantages of being binder-free include avoiding the effects of binders on conductivity, pore volume, etc. Aerogel particles, on the other hand, require binders to bond together in order to form larger functional materials, but such larger materials are not considered monoliths in this specification. Furthermore, the term “binder-free” does not exclude the use of binders entirely. For example, monolithic aerogels according to this disclosure can be fixed to another monolithic aerogel or non-aerogel material by placing a binder or adhesive on the main surface of the aerogel material. Thus, binders are used to fabricate multilayer composite materials and provide electrical contact to current collectors, but binders do not have the function of maintaining the stability of the monolithic aerogel framework itself.

[0170] As used herein, the terms “gelation” or “gel transition” refer to the formation of a wet gel from a polymer system, such as the polyimide or polyamic acid described herein. At some point in the reaction or process described herein with respect to gelation (defined as the “gelation point”), the sol loses its fluidity. In this context, gelation proceeds from an initial sol state (e.g., a solution of a salt of a polyamic acid) through a highly viscous dispersion state until the dispersion solidifies and the sol gels (gelation point), resulting in a wet gel (e.g., a polyimide or polyamic acid gel). In particular, such definitions of gelation and the gelation point are simplified and do not consider the possibility of fluidity under stress, such as the thixotropic behavior of a particular gel. In some embodiments, gelation is induced by the addition of a suitable gelation initiator. In other embodiments, gelation can be induced by removing the solvent from a solution, for example, a salt of a polyamic acid. As described herein, such solvent removal can be achieved by a variety of drying techniques, including but not limited to spray drying.

[0171] As used herein, the term “wet gel” refers to a gel in which the mobile interstitial phase within an interconnected network of pores consists primarily of a conventional solvent or a liquid phase such as water, a liquefied gas such as liquid carbon dioxide, or a combination thereof. Aerogels typically require the initial generation of a wet gel, followed by processing and extraction to replace the mobile interstitial liquid phase within the gel with air or another gas. Examples of wet gels include, but are not limited to, alcohol gels, hydrogels, ketogels, carbonogels, and any other wet gels known to those skilled in the art.

[0172] As used herein, the term “average / average particle size” is synonymous with D50, meaning that half of the particles in a population have a particle size greater than this point, and the other half have a particle size less than this point. Particle size can be measured by laser light scattering techniques or microscopy techniques. Unless otherwise indicated, the average particle size reported herein is obtained by 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.

[0173] As used herein, the term “positive electrode” is used interchangeably with “cathode.” Similarly, the term “negative electrode” is used interchangeably with “anode.”

[0174] In the context of this disclosure, the term “conductivity” refers to a measure of a material’s ability to conduct electric current, or other ability to allow electrons to flow through or within a material. Specifically, conductivity is measured as the electrical conductivity / susceptance / admittance of a material per unit size. This is typically recorded as S / m (siemens per meter) or S / cm (siemens per centimeter). The conductivity or resistivity of a material can be measured by methods known in the art, including, but not limited to, in-line four-point resistivity (using the dual-configuration test method of ASTM F84-99). In the context of this disclosure, unless otherwise specified, conductivity measurements are obtained in accordance with ASTM F84 (resistivity (R) measurement obtained by dividing voltage (V) by current (I)). In certain embodiments, the materials of the present disclosure have a 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 of any two of these values.

[0175] In the context of this disclosure, the term “capacity” refers to a specific amount of energy or charge that a battery can store. Specifically, capacity is measured as the discharge current that a battery can supply per unit mass over time. It is typically recorded as ampere-hours or milliampere-hours per gram of total electrode mass, i.e., Ah / g or mAh / g. For example, a battery with a capacity of 1 Ah can supply 1 ampere in 1 hour and 0.5 amperes in 2 hours. Thus, 1 ampere-hour (Ah) corresponds to 3,600 coulombs of charge. Similarly, the term “milliampere-hour (mAh)” also refers to a unit of storage capacity of a battery, which is 1 / 1,000 of an ampere-hour. The capacity of a battery (particularly the cathode) can be determined by methods known in the art, including, but not limited to, applying a fixed constant current load to a fully charged battery until the battery voltage reaches the discharge termination voltage, multiplying the time to reach the discharge termination voltage by the constant current to obtain the discharge capacity, and dividing the discharge capacity by the weight or volume of the electrode material. In the context of this disclosure, unless otherwise specified, capacity measurements are obtained according to these methods. Unless otherwise specified, capacity is reported in battery cycle 10.

[0176] As used herein, the term “battery cycle life” refers to the number of complete charge / discharge cycles a battery can perform before its nominal capacity falls below 80% of its initial rated capacity. Cycle life can be affected by various factors that do not significantly change over time, such as the mechanical strength of the underlying substrate, the bonding of particles within the cathode material, and the maintenance of interconnectivity of the carbon matrix. It should be noted that the fact that these factors do not actually change relatively over time is a surprising aspect of certain aspects of the present invention. Cycle life can be measured by methods known in the art, including, but not limited to, cycle tests in which a battery cell undergoes repeated charge / discharge cycles at a given current rate and operating voltage. In the context of this disclosure, measurements of cycle life are obtained according to these methods unless otherwise specified. In certain aspects of this disclosure, an energy storage device such as a battery or its electrodes has a cycle life of approximately 25 cycles or more, 50 cycles or more, 75 cycles or more, 100 cycles or more, 200 cycles or more, 300 cycles or more, 500 cycles or more, 1000 cycles or more, or in a range between any two of these values.

[0177] As used herein, the term “substantially” means, unless otherwise indicated, the majority of a characteristic, quantity, etc., referred to in relation to a particular situation (e.g., substantially pure, substantially identical, etc.), such as more than about 95%, more than about 99%, more than about 99.9%, more than 99.99%, or even 100%.

[0178] Although the term "LFP" may be referred to in this specification, the teachings of this specification are more generally applicable to lithium metal phosphates (LMPs) where the cathode material, particularly the metal, can be selected from iron (i.e., LFP, LiFePO4), vanadium, manganese, or a combination of iron and manganese. The LMPs discussed herein can include, consist of, or consist essentially of a single lithium metal phosphate (e.g., LFP) or mixtures thereof (e.g., particles of LFP and LVP, where V = vanadium). Alternatively, or in combination, the LFP materials described herein may be a continuous solid solution containing a mixture of transition metals such as LiFe 1-x Mn x PO4 (0 ≦ x ≦ 1). The term "LFP" should not be construed as being limited only to iron-containing LFP and is used in the same sense as "LMP" + carbon coating.

[0179] III. Aerogel Synthesis As outlined above in the summary, the present disclosure is directed to LMP-carbon composite particles and their synthesis. These materials, which are useful as cathode materials for lithium-ion batteries, are referred to herein as "agglomerated particles" or equivalently as agglomerated or composite microbeads. The composite particles can be formed by synthesizing the LMP particles or obtaining pre-synthesized (e.g., via commercial routes) LMP particles and combining the LMP particles with an organogel precursor.

[0180] The methods disclosed herein generally utilize polyamic acids and polyimide wetted gels that can be prepared without the use of organic solvents and without the use of organic (e.g., amine) bases. The “without the use of organic bases” reference herein to the preparation of polyamic acids and polyimide wetted gels means that carbon-based alkaline substances such as amines are not used for the solubilization of pre-formed polyamic acids in water, nor for the in-situ solubilization of polyamic acids as they are formed (i.e., by the reaction of diamines with tetracarboxylic dianhydrides). To avoid ambiguity, the reference to “organic bases” does not include carbonates and bicarbonates, nor does it include carbonates and bicarbonates containing nitrogen-containing cation species (such as ammonium or guanidinium).

[0181] References to aqueous solutions herein mean that the solution is substantially free of organic solvents. The term “substantially free” as used herein with respect to organic solvents means that no organic solvents are intentionally added and that they are not present in amounts exceeding trace amounts. For example, in certain embodiments, an aqueous solution may be characterized as containing less than 1 vol% of an organic solvent, or less than 0.1 vol%, or less than 0.01%, or even 0 vol%. These water-based methods are advantageous in reducing material and waste disposal costs and mitigating potential safety and environmental hazards.

[0182] A. Preparation of polyamic acid, polyimide gel, and aerogel materials under aqueous conditions This specification utilizes methods for preparing polyamic acid and polyimide gel materials under aqueous conditions. These methods generally involve preparing an aqueous solution of a polyamic acid salt without the use of an organic base, and subsequently converting the polyamic acid salt into a polyamic acid gel or aerogel material, a polyimide gel or aerogel material, or a corresponding carbon aerogel material. Each of these materials and its corresponding method(s) are further described below in this specification.

[0183] In one embodiment, the method comprises providing a polyamic acid and mixing the polyamic acid with a water-soluble carbonate or bicarbonate in water to provide a solution of a salt of the polyamic acid. In such embodiments, the polyamic acid is a pre-formed polyamic acid, which is either a commercially available material purchased or a material prepared from suitable diamines and tetracarboxylic anhydrides according to conventionally known techniques (such as preparation in an organic solvent solution). Suitable pre-formed polyamic acids are described below with respect to polyamic acids synthesized in situ. Suitable water-soluble carbonates or bicarbonates are described further below.

[0184] Alternatively, polyamic acids can be prepared in situ. Therefore, in another embodiment, an aqueous solution of a polyamic acid salt is prepared by reacting a water-soluble diamine with a tetracarboxylic dianhydride in the presence of a water-soluble carbonate or bicarbonate. Generally, a diamine is reacted with a tetracarboxylic dianhydride in the presence of the carbonate or bicarbonate to form a polyamic acid salt. Thus, this method involves mixing a water-soluble diamine, a water-soluble carbonate or bicarbonate, and a tetracarboxylic dianhydride in water, and reacting the components to obtain a solution of the polyamic acid salt. The polyamic acid salt contains an anionic carboxylic acid group whose charge is compensated by a cation from the carbonate or bicarbonate, and the polyamic acid salt is water-soluble. Each component used in this method (e.g., water-soluble diamine, tetracarboxylic dianhydride, water-soluble carbonate or bicarbonate, etc.) is described further below.

[0185] The order in which various components are added can vary. For example, in some embodiments, the mixing involves dissolving a water-soluble diamine in water to form an aqueous diamine solution, adding a water-soluble carbonate or bicarbonate to the aqueous diamine solution, adding a tetracarboxylic dianhydride to the aqueous solution of diamine and water-soluble carbonate or bicarbonate to form a solution, and stirring the solution at a temperature in the range of about 15 to about 60°C for a period of about 1 hour to about 4 days.

[0186] In some embodiments, the mixing comprises dissolving a water-soluble diamine in water to form an aqueous diamine solution, adding a tetracarboxylic dianhydride to the aqueous diamine solution to form a suspension, stirring the suspension at a temperature in the range of about 15 to about 60°C for a period of about 1 minute to about 24 hours, adding a water-soluble carbonate or bicarbonate to the suspension, and stirring the suspension at a temperature in the range of about 15 to about 60°C for a period of about 1 hour to about 4 days to obtain an aqueous polyamic acid solution.

[0187] In some embodiments, the mixing involves simultaneously or rapidly and sequentially adding a water-soluble diamine, a tetracarboxylic dianhydride, and a water-soluble carbonate or bicarbonate to water, and stirring the resulting mixture at a temperature in the range of about 15 to about 60°C for a period of about 1 hour to about 4 days to obtain an aqueous solution of the polyamic acid salt.

[0188] A non-restrictive, general reaction sequence is shown in Scheme 1. In some cases, the reaction generally follows Scheme 1, and the reagents and products have structures according to the formulas in Scheme 1. Scheme 1. Formation of aqueous solutions of polyamic acid salts by reaction of monomers in the presence of water-soluble carbonates or bicarbonates. [ka]

[0189] The diamines disclosed herein are generally referred to as “water-soluble diamines.” As used herein, the term “water-soluble diamine” means that the diamine has considerable solubility in water so that synthetically useful concentrations of the diamine can be obtained under the conditions under which the disclosed method is used. For example, a diamine suitable for use in the disclosed method may have solubility of at least about 0.01 g, at least about 0.1 g, at least about 1 g, or at least about 10 g per 100 mL of water at 20°C.

[0190] In some embodiments, a combination of two or more diamines can be used. A combination of diamines can be used to optimize the properties of the gel material. In some embodiments, a single diamine is used.

[0191] Referring to Scheme I, the structure of the diamine can vary. In some embodiments, the diamine has a structure according to Formula I, where Z is aliphatic (i.e., alkylene, alkenylene, alkylylene, or cycloalkylene) or aryl, as described above herein. In some embodiments, Z is an alkylene such as a C2-C12 alkylene or a C2-C6 alkylene. In some embodiments, the diamine is a C2-C6 alkanediamine, but is not limited to 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, and ethylenediamine. In some embodiments, the C2-C6 alkylene of the alkanediamine is substituted with one or more alkyl groups, such as methyl.

[0192] In some embodiments, Z is an aryl. In some embodiments, the aryldiamine is 1,3-phenylenediamine, methylenedianiline, 1,4-phenylenediamine (PDA), or a combination thereof. In some embodiments, the diamine is 1,3-phenylenediamine. In some embodiments, the diamine is 1,4-phenylenediamine (PDA).

[0193] Continuing with Scheme 1, a tetracarboxylic dianhydride is added. In some embodiments, two or more tetracarboxylic dianhydrides are added. Combinations of tetracarboxylic dianhydrides can be used to optimize the properties of the gel material. In some embodiments, a single tetracarboxylic dianhydride is added. The structure of the tetracarboxylic dianhydride can vary. In some embodiments, the tetracarboxylic dianhydride has a structure according to Formula II, where L comprises an alkylene group, a cycloalkylene group, an arylene group, or a combination thereof, as described above herein. In some embodiments, L comprises an arylene group. In some embodiments, L comprises a phenyl group, a biphenyl group, or a diphenyl ether group. In some embodiments, the tetracarboxylic dianhydride of Formula II has a structure selected from one or more structures provided in Table 1. [Table 1-1] [Table 1-2]

[0194] In some embodiments, the tetracarboxylic dianhydride is selected from the group consisting of pyromellitic dianhydride (PMDA), biphthalic dianhydride (BPDA), oxydiphthalic dianhydride (ODPA), benzophenonetetracarboxylic dianhydride (BTDA), ethylenediaminetetraacetic acid dianhydride (EDDA), 1,4,5,8-naphthalenetetracarboxylic dianhydride, and combinations thereof. In some embodiments, the tetracarboxylic dianhydride is PMDA.

[0195] The methods disclosed herein utilize water-soluble carbonates or bicarbonates. These water-soluble carbonates or bicarbonates may vary. As used herein, the term “water-soluble” with respect to a salt means that the carbonate or bicarbonate has considerable solubility in water so that synthetically useful concentrations of carbonate or bicarbonate anions can be obtained under the conditions under which the disclosed methods are used. For example, a water-soluble carbonate or bicarbonate suitable for use in the disclosed methods may have a solubility of at least about 0.1 g per 100 mL of water at 20°C, at least about 1 g per 100 mL, or at least about 10 g per 100 mL.

[0196] As used herein, the term “carbonate or bicarbonate” refers to an alkaline substance containing a carbonate or bicarbonate anion, and in particular excludes alkaline substances containing a carbon-hydrogen covalent bond (i.e., organic bases including, but not limited to, alkylamines, arylamines, and heteroaromatic amines). A water-soluble carbonate or bicarbonate suitable for use in the disclosed method may be further described as non-nucleophilic, meaning that the carbonate or bicarbonate does not participate in a chemical reaction by donating an electron pair other than as a proton acceptor.

[0197] In certain embodiments, a water-soluble carbonate or bicarbonate is a carbonate. In other specific embodiments, a water-soluble carbonate or bicarbonate is a bicarbonate. Continuing with Scheme 1, a water-soluble carbonate or bicarbonate has the general formula M2CO3 or MHCO3, where M is a cation species having a valence of +1.

[0198] In some embodiments, the cationic species M includes or is an ammonium ion, a guanidinium ion, or an alkali metal ion. In some embodiments, the cationic species M includes lithium, sodium, potassium, ammonium, guanidinium, or a combination thereof. In some embodiments, the cationic species M is lithium. In some embodiments, the cationic species M is sodium. In some embodiments, the cationic species M is potassium. In some embodiments, the cationic species M is ammonium (NH4) + ) In some embodiments, the cation species M is guanidinium (NH2-C(=NH2 + It is )-NH2).

[0199] Particularly suitable water-soluble carbonates and bicarbonates include alkali metal carbonates and bicarbonates. In some embodiments, the water-soluble carbonate or bicarbonate is selected from the group consisting of lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, and combinations thereof. In some embodiments, the water-soluble carbonate or bicarbonate is selected from the group consisting of lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate.

[0200] In some embodiments, the water-soluble carbonate or bicarbonate is selected from the group consisting of ammonium carbonate, ammonium bicarbonate, guanidinium carbonate, and combinations thereof.

[0201] The amount of water-soluble carbonate or bicarbonate added may vary, and may depend, for example, on the stoichiometry of the particular salt used. For example, a person skilled in the art would recognize that it depends on the charge associated with the particular anionic species (carbonate or bicarbonate) present in the salt. For example, sodium bicarbonate (NaHCO3) reacts with one equivalent of base (bicarbonate ion, HCO3) each capable of reacting with one proton. -) is supplied, and further supplying 1 equivalent of sodium ions for each molar equivalent of sodium bicarbonate. In contrast, sodium carbonate (Na2CO3) can react with 2 equivalents of base (carbonate ions, CO3) which can react with 2 equivalents of protons from each repeating unit of the polyamic acid. 2- ) is supplied, and 2 equivalents of sodium ions are supplied for each molar equivalent of sodium carbonate.

[0202] The amount of water-soluble carbonate or bicarbonate can be expressed as a molar ratio to other reactants (e.g., diamines). The molar ratio of water-soluble carbonate or bicarbonate to diamine may need to be optimized depending on the reactants and conditions of each set. In some embodiments, the molar ratio is chosen to maintain the solubility of the polyamic acid. In some embodiments, the molar ratio is chosen to avoid any precipitation of the polyamic acid. In some embodiments, the molar ratio of water-soluble carbonate or bicarbonate to diamine is in the range of about 1 to about 4, or about 2 to about 3. In some embodiments, the molar ratio is from about 1.0, about 1.1, about 1.2, about 1.3, about 1.4, or about 1.5 to about 1.6, about 1.7, about 1.8, about 1.9, or about 2.0. In some embodiments, the molar ratio of the water-soluble carbonate or bicarbonate to the diamine is about 2.0 to about 2.6, for example, about 2.0, about 2.1, about 2.2, about 2.3, about 2.4, about 2.5, or about 2.6. While we do not wish to be bound by any particular theory, in some exemplary embodiments, it is considered that at least a sufficient amount of base is required to enable the neutralization of substantially all free carboxylic acid groups of the polyamic acid (i.e., to form a salt). In some embodiments, the amount of water-soluble carbonate or bicarbonate used is the amount that neutralizes substantially all carboxylic acid groups present in the polyamic acid formed during the reaction.

[0203] In some embodiments, the water-soluble salt is a carbonate such as lithium carbonate, sodium carbonate, potassium carbonate, ammonium carbonate, or guanidinium carbonate, with a molar ratio of carbonate ions to diamine of approximately 1.0 to approximately 1.3.

[0204] In some embodiments, the water-soluble carbonate or bicarbonate is a bicarbonate such as lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, or ammonium bicarbonate, and the molar ratio of bicarbonate ions to diamine is approximately 2.0 to approximately 2.6.

[0205] In some embodiments, the amount of water-soluble carbonate or bicarbonate present can be expressed in comparison to the carboxylic acid groups of the polyamic acid that are formed during the reaction or otherwise present in the reaction mixture. In some embodiments, the water-soluble carbonate or bicarbonate is a bicarbonate such as lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, or ammonium bicarbonate, and the molar ratio of bicarbonate ions to carboxylic acid groups of the polyamic acid is about 2.0. In some embodiments, the water-soluble carbonate or bicarbonate is a carbonate such as lithium carbonate, sodium carbonate, potassium carbonate, or ammonium carbonate, and the molar ratio of carbonate ions to carboxylic acid groups of the polyamic acid is about 1.0.

[0206] The relative amounts of the diamine and dianhydride present can be expressed as a molar ratio. The molar ratio of diamine to dianhydride may vary depending on the desired reaction time, reagent structure, and desired material properties. In some embodiments, the molar ratio is about 0.1 to about 10, for example, about 0.1 and about 0.5 or about 1 to about 2, about 3 and about 5 or about 10. In some embodiments, this ratio is about 0.5 to about 2. In some embodiments, this ratio is about 1 (i.e., stoichiometric), for example, about 0.9 to about 1.1. In certain embodiments, this ratio is about 0.99 to about 1.01.

[0207] The molecular weight of polyamic acid can vary depending on the reaction conditions (e.g., concentration, temperature, reaction time, properties of the diamine and dianhydride). The molecular weight is based on the number of repeating units of the polyamic acid, as indicated by the integer value "n" for the structure of Equation III in Scheme 1. The specific molecular weight range of the polymer material produced by the disclosed method can vary. In general, without particularly considering the molecular weight, the above reaction conditions can be modified to obtain gels with desired physical properties. In some embodiments, a surname for molecular weight is provided by the viscosity of the polyamic acid solution, which is determined by variables such as temperature, concentration, molar ratio of reactants, and reaction time.

[0208] The temperature at which the reaction takes place can vary. A suitable range is generally about 4°C to about 100°C. In some embodiments, the reaction temperature is about 15 to about 60°C, for example, about 20, about 25, about 30, about 35, about 40, about 45, about 50, about 55, or about 60°C. In some embodiments, the temperature is about 15 to about 25°C. In some embodiments, the temperature is about 50 to about 60°C.

[0209] The reaction is allowed to proceed for a certain period of time, generally until all available reactants (e.g., diamines and dianhydrides) have reacted with each other. The time required for the reaction to be completed can vary depending on the structure, concentration, and temperature of the reagents. In some embodiments, the reaction time is about 1 minute to about 1 week, for example, about 15 minutes to about 5 days, about 30 minutes to about 3 days, or about 1 hour to about 1 day. In some embodiments, the reaction time is about 1 hour to about 12 hours.

[0210] The concentration of polyamic acid salts in aqueous solutions can vary. For example, in some embodiments, the concentration range of polyamic acid salts in aqueous solutions is approximately 0.01 to approximately 0.3 g / cm³, based on the weight of the polyamic acid. 3 That is the case.

[0211] B. Gels of polyamic acid (PAA) and polyimide (PI) In some embodiments, this method further includes converting an aqueous solution of a polyamate salt into a corresponding polyamate gel. Generally, a method for converting a polyamate solution into a corresponding polyamate gel involves acidifying the polyamate solution to convert the polyamate salt into polyamate, and then phase-separating the polyamate as a wet organogel. Acidification for forming polyamate generally follows Scheme 2.

[0212] The method of acidification may vary. For example, in some embodiments, the polyamate salt solution is added to an acid solution, where the acidification of the polyamate salt solution is rapid. Alternatively, the polyamate salt solution may be acidified by adding an acid to the polyamate salt solution. In some embodiments, the polyamate salt solution may be gradually or slowly acidified using conditions or techniques known to those skilled in the art.

[0213] The acids used may vary. For example, mineral acids or organic acids can be used. Suitable acids include, but are not limited to, hydrochloric acid, sulfuric acid, phosphoric acid, or carboxylic acids such as acetic acid. Alternatively, acid precursors can be used, meaning materials that produce acids under specific conditions. One non-limiting example of such an acid precursor is acetic anhydride, which releases acetic acid upon hydrolysis in contact with water. Scheme 2. Formation of polyamic acid gel by reaction of polyamic acid salt with acid. [ka]

[0214] In some embodiments, polyamic acid-wet gels prepared as disclosed herein, or the corresponding aerogels described below, contain residual carbonates or bicarbonates. Generally, the residual amounts are trace, but the carbonates or bicarbonates and / or associated countercations (e.g., alkali metal ions, guanidinium ions, etc.) can be detected by analytical methods known to those skilled in the art.

[0215] Next, the obtained polyamic acid gel material can be dried to form a polyamic acid aerogel. Methods for acidifying and forming the polyamic acid gel material are described, for example, in International Patent Application Publication No. WO2022125835, which are incorporated herein by reference. A drying method for forming the corresponding aerogel is described further below.

[0216] In some embodiments, the method further comprises forming a polyimide aerogel from an aqueous solution of a polyamic acid salt. Generally, the method comprises imidizing the polyamic acid salt to form a polyimide gel and drying the polyimide gel to form a polyimide aerogel. A method for imidizing an aqueous solution of a polyamic acid salt is described, for example, in International Patent Application PCT / US2021 / 062706 (which is incorporated herein in its entirety), and suitable methods are further described below. A drying method for forming the corresponding polyimide aerogel is further described below.

[0217] In some embodiments, imidation of a polyamic acid salt involves thermal imidation of the corresponding polyamic acid. Irradiation of a wet gel polyamic acid material with microwave frequency energy is one particularly suitable heat treatment. Compared to conventional heating which relies on slow heat conduction, microwave heating allows for rapid and efficient energy transfer. Therefore, microwave heating is particularly suitable for carrying out the thermal imidation reaction of the present invention. Generally, the power and duration of microwave frequency irradiation are sufficient to convert a substantial portion of the amide and carboxyl groups of the polyamic acid into imide groups. Where used herein in relation to converting amide and carboxyl groups into imide groups, “a substantial portion” means that more than 90% of the amide and carboxyl groups, e.g., 95%, 99%, 99.9%, 99.99%, or even 100%, are converted into imide groups.

[0218] In other embodiments, imidation of a polyamic acid salt involves performing chemical imidation, which includes adding a gelling initiator to an aqueous solution of a salt of the polyamic acid to form a gelling mixture ("sol"), and gelling the gelling mixture (for example, in a mold, or by pouring it onto a sheet, or in various other forms such as beads). In such embodiments, a gelling initiator is added to initiate and promote imidation to form a polyimide wet gel from the polyamic acid salt.

[0219] The structure of gelation initiators can vary, but generally, they are reagents that are at least partially soluble in the reaction solution while exhibiting minimal reactivity with aqueous solutions, and that react with the carboxylic acid groups of polyamic acids, effectively promoting the imidation of the carboxyl and amide groups of polyamic acids. Examples of suitable gelation initiators include carboxylic acid anhydrides such as acetic anhydride and propionic anhydride. In some embodiments, the gelation initiator is acetic anhydride.

[0220] 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 with tetracarboxylic dianhydride in various molar ratios. In some embodiments, the gelling initiator is present with polyamic acid in various molar ratios. 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, for example, about 2, about 3, about 4 or about 5 to about 6, about 7, about 8, about 9 or about 10. In some embodiments, this ratio is about 2 to about 5.

[0221] The temperature at which the gelation reaction proceeds can vary, but is generally below approximately 50°C, for example, between approximately 10 and 50°C, or between approximately 15 and 25°C.

[0222] The gelation conditions described above (both acidification and imidization) are general and are intended to be non-limiting in terms of the method by which gelation is carried out. For example, those skilled in the art will recognize various permutations in which monoliths or beads (including microbeads) are prepared. For example, this specification considers methods for forming monoliths by pouring a gelling mixture into a mold, forming beads of various sizes by dropping or spraying a polyamic acid solution into an acid-receiving solution, or forming micron-sized beads of polyamic acid or polyimide gel in an emulsion.

[0223] In some embodiments, the polyimide wetted gels prepared as disclosed herein, or the corresponding aerogels described below, contain residual carbonates or bicarbonates. Generally, the residual amounts are trace, but the carbonates or bicarbonates and / or associated countercations (e.g., alkali metal ions, guanidinium ions, etc.) can be detected by analytical methods known to those skilled in the art.

[0224] C. Polyamic acid and polyimide aerogel As described above herein, in some embodiments, the method further comprises converting a polyamic acid salt into an aerogel material via a corresponding polyamic acid or polyimide wet gel. Generally, the formation of an aerogel involves drying the wet gel in one or more steps. In some embodiments, the wet gel (polyamic acid or polyimide) is aged. After aging, the resulting wet gel material can be collected (e.g., removed from a mold), first washed or desolvent-changed with water to remove any unreacted organic salts or acids, and then the primary reaction solvent (i.e., water) present in the wet gel can be replaced with a suitable secondary solvent. Such a secondary solvent must be miscible with supercritical fluid carbon dioxide (CO2) and may include linear alcohols having one or more aliphatic carbon atoms, diols having two or more carbon atoms, or branched alcohols, cyclic alcohols, alicyclic alcohols, aromatic alcohols, polyols, ethers, ketones, cyclic ethers, or derivatives thereof. In some embodiments, the secondary solvent is water, C1-C4 alcohols (e.g., methanol, ethanol, propanol, isopropanol, or n-, iso-, or sec-butanol), acetone, tetrahydrofuran, ethyl acetate, acetonitrile, supercritical fluid carbon dioxide (CO2), or a combination thereof. In some embodiments, the secondary solvent is ethanol.

[0225] Once a wet gel is formed and processed, the liquid phase of the wet gel can then be extracted at least partially from the wet gel material using an extraction method that includes processing and extraction techniques to form an aerogel material (i.e., "dry"). Liquid phase extraction plays a crucial role in designing the properties of the aerogel, such as porosity and density, and related properties such as thermal conductivity, among many other factors. Generally, aerogels are obtained when the liquid phase is extracted from the wet gel in a manner that causes low shrinkage in the porous network and solid framework of the wet gel. Aerogels or xerogels can be obtained by drying the wet gel using various techniques. In exemplary embodiments, the wet gel material can be dried under ambient pressure, under vacuum (e.g., by freeze-drying), under subcritical or supercritical conditions to form the corresponding dry gel (e.g., aerogel such as xerogel).

[0226] In some embodiments, it may be desirable to reduce the surface area of ​​the dry gel. When a reduction in surface area is desirable, the aerogel can be converted completely or partially into a xerogel with varying porosity. The high surface area of ​​the aerogel can be reduced by forcibly breaking down some of the pores. This can be done, for example, by immersing the aerogel in a solvent such as ethanol or acetone for a certain period of time, or by exposing the aerogel to solvent vapor. The solvent is then removed by drying under ambient pressure.

[0227] Aerogels are typically formed by removing the liquid mobile phase from a wet gel material at or above the critical temperature and pressure of the liquid mobile phase. Upon reaching (near critical) or exceeding the critical point (supercritical, i.e., the system's pressure and temperature exceed the critical pressure and temperature, respectively), a new supercritical phase distinct from the liquid or vapor phase appears in the fluid. The solvent can then be removed without introducing any associated mass transfer limitations typically associated with the liquid-vapor interface, capillary forces, or receding liquid-vapor boundary. Furthermore, the supercritical phase generally exhibits higher miscibility with organic solvents, thus enabling better extraction. Co-solvents and solvent exchange are also commonly used to optimize the supercritical fluid drying process.

[0228] When evaporation or extraction occurs below the supercritical point, capillary forces generated by the evaporation of the liquid can cause shrinkage and pore collapse within the gel material. Maintaining the mobile phase near or above the critical pressure and temperature during the solvent extraction process mitigates these adverse effects of capillary forces. In certain embodiments of this disclosure, using near-critical conditions just below the critical point of the solvent system may enable the production of aerogels or compositions with sufficiently low shrinkage, thus producing commercially viable end products.

[0229] To provide aerogels, wet gels can be dried using various techniques. In exemplary embodiments, wet gel materials can be dried under ambient pressure, subcritical conditions, or supercritical conditions.

[0230] Gel materials can be dried at ambient pressure using both room temperature and high-temperature processes. In some embodiments, a slow atmospheric pressure drying process can be used, in which the wet gel is exposed to air in an open container for a period sufficient to remove the solvent, for example, ranging from several hours to several weeks, depending on the solvent, the amount of wet gel, the exposed surface area, the size of the wet gel, etc.

[0231] In another embodiment, the wet gel material is dried by heating. For example, the wet gel material can be heated in a convection oven for a certain period of time to evaporate most of the solvent (e.g., ethanol). After partial drying, the gel can be left at ambient temperature for a certain period of time, for example, several hours to several days, to dry completely. This drying method produces a xerogel. In particular, according to this disclosure, drying a monolithic wet gel results in cracking, but a bead-shaped wet gel has a low target density Td (e.g., Td = 0.05 g / cm³). 3 It was found that the spherical shape is maintained even in solution.

[0232] In some embodiments, the wet gel material is dried by freeze-drying. "Freeze-drying" or "lyophilizing" means a low-temperature process for removing a solvent, which includes freezing the material (e.g., the wet gel material), reducing the pressure, and then removing the frozen solvent by sublimation. Water is an ideal solvent for removal by freeze-drying, and since water is the solvent in the methods disclosed herein, freeze-drying is particularly suitable for aerogel formation from the disclosed polyimide wet gel material. This drying method produces cryogels, which may closely resemble aerogels.

[0233] Wet gel materials can be dried using both supercritical and subcritical drying. In some embodiments, wet gel materials are dried under subcritical or supercritical conditions. In an exemplary embodiment of supercritical drying, the gel material can be placed in a high-pressure vessel to extract the solvent with supercritical CO2. After removing the solvent, for example ethanol, the vessel can be held above the critical point of CO2 for a certain period, for example about 30 minutes. After supercritical drying, the vessel is depressurized to atmospheric pressure. Generally, aerogels are obtained by this process.

[0234] In an exemplary embodiment of subcritical drying, the gel material is dried using liquid CO2 at a pressure ranging from about 800 psi to about 1200 psi at room temperature. This operation is faster than supercritical drying; for example, the solvent (e.g., ethanol) can be extracted in about 15 minutes. Generally, aerogels are obtained by this process.

[0235] Several additional aerogel extraction techniques are known in the art, including various approaches using supercritical fluids for drying aerogels, as well as atmospheric pressure drying techniques. For example, U.S. Patent No. 6,670,402 teaches the extraction of a liquid phase from a gel via rapid solvent exchange by injecting supercritical (but not liquid) carbon dioxide into an extractor preheated and prepressurized to substantially supercritical conditions or higher, thereby producing an aerogel.

[0236] In some embodiments, supercritical CO2 conditions are used to extract the liquid phase from the wet gel.

[0237] IV. LFP-Aerogel Agglomerated Particles A. Exemplary process flow for aggregate particle synthesis Figures 1, 2, 3, and 4 are flowcharts illustrating several methods according to non-limiting embodiments of the present disclosure. According to Figure 1, in one embodiment, method 100 is used to synthesize aggregate particles embedded with LMP particles. In step 102, an aqueous solution of polyamic acid salt is prepared, and in step 104, cathode material particles are mixed. In step 106, organogel formation is initiated to form a polyamide organogel by adding a gelling initiator, such as an acid or acid anhydride, to the mixture. In step 108, the gelling mixture from step 106 is emulsified to form beads before gel formation is complete, and after gelling, the beads are separated and washed in step 110. Next, the beads can be dried in step 112 to form LMP-embedded aerogel or xerogel beads. Then, the beads are carbonized in step 114 to form aggregate particles of the present disclosure.

[0238] Alternatively, according to method 200 in Figure 2, an aqueous solution of polyamic acid salt is prepared in step 202, and cathode material particles are mixed in step 204. In step 206, a gelling initiator, such as an acid anhydride, is added to the mixture, and in step 208, a gel is formed from the mixture in a mold. The monolithic gel formed in step 208 is pulverized in step 210 and optionally dried in step 212 to form an aerogel or xerogel powder. In step 214, this powder is carbonized to form aggregate particles according to the present disclosure in powder form.

[0239] Figure 3 shows a further alternative method 300 for forming aggregate particles according to the present disclosure in the form of beads. According to this process 300, in step 302 an aqueous solution of polyamic acid salt is prepared and in step 304 cathode material particles are mixed in. After emulsifying the mixture in step 306, a gelling initiator such as an acid is added in step 308 to gel the emulsion. In step 310 the beads of the formed gel are separated and washed and then dried in step 312 to form aerogel or xerogel beads with cathode material particles embedded in them. These beads are then carbonized in step 314 to form aggregate particles according to the present disclosure.

[0240] A further alternative is shown in Figure 4, which is labeled as process 400. In this embodiment, an aqueous solution of polyamic acid salt is prepared in step 402. In step 404, particles of cathode material are mixed. In step 406, the mixture is dried, for example, by spray drying, to form intermediate xerogel beads and / or powder. Next, in step 408, the intermediate xerogel beads and / or powder are carbonized to form aggregate particles according to the present disclosure.

[0241] B.LFP synthesis As described herein, the LMP (M = metal, also referred to as "LFP") materials discussed herein include, consist of, or essentially consist of, a single lithium metal phosphate (e.g., LFP where "F" is iron), or mixtures thereof (e.g., particles of LFP and LVP, where V = vanadium). Alternatively, or in combination, the LFP materials described herein may be LiFe 1-x Mn x It may also be a continuous solid solution containing a mixture of transition metals such as PO4 (0 ≤ x ≤ 1). When the metal is Fe or Mn, the chemical formula is LiMePO4. When the metal is V, the chemical formula is Li3V2(PO4)3.

[0242] This disclosure allows for the use of LMPs, including LFPs from any source, including commercial sources, and coarse-grained, low-cost LFPs with large particle size and low electrochemical performance ("LC-LFP"). However, for illustrative purposes, a schematic method for synthesizing LMPs is also provided.

[0243] LFPs can be synthesized from metal oxide precursor materials. For M=Fe, natural or artificial Fe2O3 is selected as the precursor for reasons of cost, availability, and low toxicity. For M=Mn, the precursor may be MnO, Mn2O3, MnO2, or a combination thereof. For M=V, the precursor may be V2O3, VO2, V2O5, or a combination thereof. If the average oxidation state of the precursor metal oxide exceeds 2.0 for Mn and Fe precursors, and 3.0 for V precursors (i.e., all those described in this paragraph except MnO and V2O3), a carbon source is required during LFP synthesis to quantitatively and stoichiometrically reduce the metal to the Me(II) oxidation state.

[0244] The choice of carbon source varies depending on the polymer source, which may include synthetic polymers (polyarylamides, polyimides, polyamides, polybenzoxazines (PBOs), phenol-formaldehyde, RF, polyvinylpyrrolidone, polyethylene oxide, polyethylene), biopolymers (starch, cellulose), modified biopolymers (alginic acid, cellulose acetate, carboxymethylcellulose [CMC], sucrose-citric acid polyester), biomass, or simple monosaccharides or disaccharides (sucrose, glucose, fructose).

[0245] In the case of LiMnPO4 synthesized from MnO as a precursor, large-scale reduction by a carbon source is not necessary due to the Mn(II) oxidation state. In such cases, a thickener such as CMC or alginic acid is added up to 0.5% (by weight relative to MnO) to keep the components suspended throughout the drying process and provide additional protection to prevent accidental oxidation during the heating process (e.g., O2 leakage or impurities in the carrier gas).

[0246] In all cases, depending on the choice of carbon source, an appropriate amount of carbon source is added so that the residual carbon content of the bulk LMP is 0.1 to 3% by weight.

[0247] A typical LMP synthesis proceeds as follows: H3PO4 85%, H2O (weight ratio of 1:1 to 10:1 relative to the oxide source), Li2CO3, metal oxide, and carbon source / thickener are added to the reaction vessel in any order such that the molar ratio of Li:Fe:P is 1:1:1. Mixing can be carried out using various techniques such as overhead mechanical mixing, high-speed blade mixers, ultrasonic mixers, and recirculation mixers, and the mixing time is from 15 minutes to 10 hours.

[0248] Drying can be carried out in various forms, including hot plates, air ovens, forced high-temperature gas dryers (air or N2), conveyor belt ovens, vacuum ovens, tumble dryers, or combinations of the above. The drying temperature ranges from room temperature to 200°C.

[0249] Next, the dried LMP is heat-treated in a temperature range of 300 to 1000°C, using various heating methods such as conventional furnaces (convection / conduction), microwave furnaces, or induction furnaces. Heating times vary from a few minutes to several hours depending on the heating method. Microwave and induction heating are used for short heating times, while conventional furnaces are used for longer heating times. Heating and cooling rates can be 1 to 1000°C / min depending on the heating method.

[0250] The furnace atmosphere may be static or dynamic, provided by gas flow or vacuum. In the case of gas flow, an inert (Ar or N2) or reducing (H2-Ar or H2-N2 with a hydrogen content of 5-10% mol) gas mixture can be used at a flow rate of 10 mL / min to 10 L / min per kg of reaction charge. If a reducing atmosphere is present, the required amount of reducing carbon (C) decreases proportionally.

[0251] Heating can also be carried out in air using equipment that minimizes O2 leakage into the reaction mixture, such as a muffle furnace under nitrogen purging or a sealed furnace with an inert or reducing gas blanket. In such cases, oxygen absorbers such as carbon felt can be used on the reaction charge to minimize oxidation of LMP / C.

[0252] C.LMP grinding Grinding of LMP to reduce particle size can be performed using various grinders such as roller mills, planetary ball mills, or high-speed bead agitation mills, with grinding media such as alumina, zirconia, and stainless steel. Grinding times can vary from a few minutes (high-energy grinders) to several hours (low-energy grinders). Rotation speed can vary from 60 to 10,000 rpm depending on the method.

[0253] The grinding can be carried out in a dry or wet form. In the case of the wet grinding method, the bulk LMP powder is dispersed in a liquid phase selected from water, ethanol, isopropanol, ethylene glycol, acetone, or a mixture thereof. The liquid / solid weight ratio can vary from 0.5:1 to 10:1. The weight ratio of the grinding medium (balls or rings) to the solid can vary from 5:1 to 100:1.

[0254] The grinding can be carried out in a static (batch) mode or a dynamic (flow) mode using a single or multiple circuit paths in air or an inert gas atmosphere. In the case of wet grinding, the obtained grinding slurry can be used directly for mixing with the polyamic acid salt, or dried at a drying temperature in the range of ambient temperature (e.g., about 20°C) to 200°C according to one of the methods described above, i.e., using a hot plate, an air oven, a forced high-temperature gas dryer (air or N2), a conveyor belt oven, a vacuum oven, a tumble dryer, or a combination thereof. The dispersant can be recycled and reused as needed. In the case of wet grinding, the grinding can be carried out with or without a surfactant. The surfactant can vary in the range of 0.1 to 5% by weight based on the solid bulk LMP filling amount.

[0255] After grinding, the desired average particle size of the LMP is less than 250 nm, for example less than 150 nm, referring to the D50 described herein.

[0256] D. Dispersion of LMP into the Gel Precursor An aqueous solution of polyamic acid salt is prepared as described above. An aqueous solution of polyamic acid salt can be prepared as the first step of the disclosed method using any of the methods described herein. For example, the polyamic acid salt can be prepared in situ from a suitable diamine and tetracarboxylic dianhydride in water as described herein, or the polyamic acid can be prepared separately in a non-aqueous solvent (e.g., dimethylformamide or dimethylacetamide) and dissolved in water using a water-soluble carbonate or bicarbonate as described herein. The inventors have found that among the methods disclosed herein, particularly advantageous results are obtained when an aqueous solution of polyamic acid salt is formed using a guanidinium carbonate salt or a guanidinium bicarbonate salt and / or a lithium carbonate salt or lithium bicarbonate salt.

[0257] The dispersion of nanoscale LMPs into a gel precursor solution (i.e., an aqueous solution of polyamic acid salt) can be achieved using various methods such as high-speed mixers, high-shear mixers, ball mills, or rotary mixers. The solid-liquid mixing ratio, polymer solution concentration, selection of polymer chemistry, and mixing conditions are described in the examples. Generally, the mixing conditions are selected based on several factors, including scale, type of organogel, and its concentration. Generally, mixing is carried out for a sufficient period and under conditions to disperse the LMP material in the gel precursor solution.

[0258] For example, in some embodiments, mixing is carried out at a speed of at least about 500 rpm, e.g., about 500 to about 5000 rpm. In some embodiments, mixing is carried out at a higher speed, such as about 1000 to about 9000 rpm, for example, using a homogenizer. Such high-speed mixing is particularly useful when the method involves forming an emulsion to produce an organogel in which LMP is dispersed in the form of beads. In some embodiments, mixing is carried out for a period ranging from about 1 minute to about 30 minutes, e.g., about 1 minute to about 3 minutes, about 4 minutes to about 15 minutes, or about 5 minutes to about 10 minutes. Those skilled in the art will recognize that the mixing speed and mixing time can be varied depending on the desired degree of dispersion / emulsification.

[0259] According to this disclosure, the viscosity of the gel precursor is found to play a particularly important role in providing advantageous aggregated particles. In particular, the density of the gel precursor solution should be sufficient to maintain the nanoscale LMP particles in a dispersed state and to separate them from one another so that they remain separated in the resulting organogel. Approximately 0.05 g / cm³ 3 The concentration (mass of polymer precursor solute per gram of water) may be particularly advantageous in providing proper dispersion of LMP particles.

[0260] It is also possible to grind bulk LMP powder in an aqueous polyamic acid solution. In this case, the "grinding" and "dispersion" steps are integrated, eliminating the need for separate dispersion. This is because the polyelectrolyte properties of the polyamic acid solution have a high affinity for wetting the oxide-terminated surfaces of the ground LMP particles.

[0261] The disclosed method includes the step of mixing a cathode material containing LMPs (e.g., iron, manganese, vanadium, or combinations thereof) with an aqueous solution of a polyamic acid salt to form a slurry. The slurry is then gelled and dried to form an aerogel or xerogel. The amount of LMPs in the slurry depends on the target ratio of LMPs to aerogels in the final product. LMPs can be obtained from any source, preferably from low-cost sources (LC-LFPs), as described above, but in the context of this disclosure, it is important to add LMPs to form a slurry of nanoscale particles. These can be obtained by grinding bulk LMP material, for example, by reducing the average particle size of a commercially available product from the micron scale to the submicron and nanoscale.

[0262] Grinding can be carried out using wet or dry processes. In a dry grinding process, the powder is added to a container along with a grinding medium. The grinding medium typically includes balls or rods of zirconium oxide (yttrium stabilized), silicon carbide, silicon dioxide, quartz, or stainless steel. The particle size distribution of the resulting grinding material is controlled by the energy applied to the system and by matching the particle size of the starting material to the size of the grinding medium. However, dry grinding is an inefficient and energy-consuming process. Wet grinding is similar to dry grinding, but a grinding liquid is added. The advantage of wet grinding is that the energy consumption to obtain the same results is 15-50% lower than that of dry grinding. A further advantage of wet grinding is that the grinding liquid can protect the grinding material from oxidation. Wet grinding can also produce finer particles and has been found to have less particle aggregation. Therefore, in some embodiments, this method includes wet grinding.

[0263] Wet grinding can be carried out using a variety of liquid components. In other embodiments, the grinding liquid or components contained in the grinding liquid are selected to provide desired surface chemical functionalization of particles (e.g., LFP particles) during or after grinding. The grinding liquid or components contained in the grinding liquid may also be selected to control the chemical reactivity or crystalline morphology of the particles (e.g., LFP particles). In exemplary embodiments, the grinding liquid or components contained in the grinding liquid may be selected based on compatibility or reactivity with downstream materials, processing steps, or applications of the particles (e.g., LFP particles). For example, the grinding liquid or components contained in the grinding liquid may be compatible with, useful in, or identical to, a liquid or solvent used in a process for forming or producing organic or inorganic aerogel materials. In yet another embodiment, the grinding liquid may be selected so that the grinding liquid or components contained in the grinding liquid produce a coating on the surface of the LFP particles or on intermediate species such as aliphatic or aromatic hydrocarbons, or by crosslinking or producing cross-functional compounds that react with organic or inorganic aerogel materials.

[0264] In some embodiments, the solvent or mixture of solvents used in wet grinding can be selected to control the chemical functionalization of the particles during or after grinding. In some embodiments, LMPs can be conveniently ground in situ in a solution of polyamic acid salt used to form a gel in the disclosed method. In this particular embodiment of the method, there is no need to perform a separate step of dispersing the ground LMP particles in a solution of polyamic acid salt, because this is already achieved in the grinding process. The polyamic acid solution can wet the oxide-terminated surfaces of the ground LMP particles and achieve excellent uniform dispersion of LFP particles in the slurry.

[0265] E. Gelation for organogel formation Processes for forming organogels by gelling aqueous solutions of polyamic acid salts are described herein in a section entitled “Preparation of Polyamic Acid and Polyimide Gel Materials under Aqueous Conditions,” and any of these methods can be used to form the gels of this disclosure from an aqueous slurry of a polyamic acid solution and LMP. The following processes 1, 2, and 3 are constructible for the synthesis of aerogel microbeads and / or xerogel microbeads. Aerogel and / or xerogel microbeads can be selected for production in these processes by adjusting the processing temperature, solvent, solvent evaporation rate, reaction rate, drying rate, and other factors to maintain or reduce the porosity of the wet gel (e.g., through pore collapse during drying).

[0266] i. Process 1: Polyimide (PI) gel beads Using a high-speed mixer, the nano-sized LMPs obtained by grinding are uniformly dispersed in an appropriate amount (depending on the target LMP / C aerogel ratio) of an aqueous polyamic acid salt for 5 to 15 minutes at 1000 to 5000 rpm.

[0267] Acetic anhydride is added to the resulting slurry as a gelling initiator, and the mixture is poured into an aqueous, miscible medium (i.e., a dispersion medium such as mineral spirits, hexane, heptane, kerosene, octane, or other hydrocarbons), and the mixture is emulsified at high speed (1000-9000 rpm) using a homogenizer. During this process, micron-sized (5-30 μm) LMP / PI wetted gel beads are formed. The emulsification process lasts for 4-15 minutes.

[0268] The synthesis of LMP / PI wetted gel beads can be carried out with or without a surfactant. When using a surfactant, the surfactant is dissolved in an immiscible dispersion medium (1-2% by weight) before adding the acidified LMP / polyamic acid solution slurry.

[0269] The dispersion medium is separated from the beads primarily by decantation. The dispersant is recyclable. The LMP / PI gel beads are washed several times with ethanol to remove trace amounts of dispersion medium. Subsequently, the LMP / PI gel beads are converted to LMP / PI aerogel or xerogel beads by drying.

[0270] ii. Process 2: Polyamic acid (PAA) gel beads For LMP / PAA bead synthesis, the above slurry is poured into a non-aqueous, water-immiscible dispersion medium (mineral spirits, hexane, heptane, kerosene, octane, or other hydrocarbons) and emulsified at high speed (1000-9000 rpm) using a homogenizer. After mixing for 1-3 minutes (during which time micron-sized (5-30 μm) liquid beads are formed from the aqueous slurry), acetic acid or acetic anhydride is added to the mixture (while mixing) to induce gelation of the formed beads.

[0271] LMP / PAA bead synthesis can be carried out with or without a surfactant. When a surfactant is used, the surfactant is dissolved in the dispersion medium (1-2% by weight) before adding the LMP / polyamic slurry. The dispersion medium is separated from the beads mainly by decantation. The dispersant is recyclable. The LMP / PAA gel beads are washed several times with ethanol to remove trace amounts of dispersion medium. Subsequently, the LMP / PAA gel beads are converted to LMP / PAA aerogel or xerogel beads by drying.

[0272] iii. Process 3: Polyimide (PI) Gel Monolith Using a high-speed mixer, the pulverized nano-sized LMPs are uniformly dispersed in an appropriate amount (depending on the target LMP / C aerogel ratio) of an aqueous polyamic acid salt solution at 1000-5000 rpm for 5-15 minutes. The resulting slurry is gelled by adding an appropriate amount of acetic anhydride while mixing (using mechanical, magnetic, or other mixing means). The wet monolithic gel (LMP / PI) can be pulverized into small gel chunks (mm size) before supercritical drying (to form an aerogel) or conventional atmospheric pressure drying (to form a xerogel).

[0273] The resulting LMP / PI aerogel (or xerogel) material can be further ground into a powder consisting of micron-sized particles (<50 μm) using a low-energy pulverizer. As a whole, the average particle size D50 of the beads or particles produced by Processes 1, 2, and 3 is preferably 0.5 to 20 microns, more preferably about 1 micron to 10 microns, for example 5 microns. If the particle size is less than 1 micron, it can be easily dispersed in the liquid binder / carbon additive during electrode casting and can be easily cast as a film of uniform thickness by blade casting technology, so the reproducibility of the air density required for anode / cathode pairing is high, but there are certain drawbacks (if it is too small, it becomes difficult to work due to the influence of dust and static electricity, etc., and generally the tap density of the powder becomes low (shape-dependent), and the energy density becomes low). In contrast, a particle size exceeding 10 microns is difficult to cast uniformly, leading to fluctuations in the air capacity of the electrode, and also having a particulate / coarse appearance, which may cause holes in the separator during battery assembly or when stack pressure is applied).

[0274] F. Spray Drying The following process has been experimentally found to mainly produce xerogel microbeads. In an alternative method according to the present disclosure, the aqueous solution of polyamic acid salt does not undergo the gelation process described above. Instead, the LMP particles are dispersed in the aqueous solution of polyamic acid salt as described above, and the resulting slurry is spray dried using techniques known in the art. This includes spraying the slurry while heating to produce small droplets with a relatively large surface area that dry immediately. Thereby, beads of dried droplets containing cathode material particles and polymer are obtained. By controlling the nozzle of the spray drying device and the relative flow rates of the feed (slurry) and the drying gas, agglomerated particles having a size of 5 to 30 μm can be obtained. In this way, the formed agglomerated particles contain particles of the cathode material at least partially encapsulated by the polymer from the solution.

[0275] G. Carbonization In some embodiments, the method further comprises converting an organogel (e.g., polyamic acid or polyimide aerogel) into an isomorphic carbon aerogel, the conversion comprising thermal decomposition of the respective aerogel under suitable conditions. Thus, in some embodiments, the method further comprises thermal decomposition (e.g., carbonization) of the polyamic acid or polyimide aerogel disclosed herein, which means heating the aerogel at a temperature and time sufficient to convert substantially all of the organic material into carbon. Where used herein in relation to thermal decomposition, “substantially all” means that more than 95% of the organic material is converted into carbon, e.g., 99%, 99.9%, 99.99%, or even 100% of the organic material is converted into carbon. When an organic aerogel is thermally decomposed, the aerogel is converted into an isomorphic carbon aerogel in which the physical properties (e.g., porosity, surface area, pore size, diameter, etc.) are substantially retained within the corresponding carbon aerogel.

[0276] The time and temperature required for thermal decomposition can vary. In some embodiments, the polyimide aerogel is exposed to a processing temperature of about 600°C or higher, for example, about 600°C, about 650°C, about 700°C, about 750°C, about 800°C, about 850°C, about 900°C, or about 950°C, or in the range of any two of these values, for the carbonization of the aerogel. Generally, thermal decomposition is carried out under an inert atmosphere to prevent combustion of the organic or carbon material. Suitable atmospheres include, but are not limited to, nitrogen, argon, or a combination thereof. In some embodiments, thermal decomposition is carried out under nitrogen.

[0277] Aggregate particles, including, for example, aerogels, xerogels, or spray-dried particles, manufactured by the above method are further carbonized as described above. This requires heating the material for a sufficient time to convert substantially all of the organic material (polymer) into carbon. As described above, pyrolysis (carbonization) can be carried out at a variety of temperatures from above 650°C to 1000°C. According to this disclosure, a temperature of 800°C has been found to be particularly advantageous for pyrolysis of the disclosed aggregate particles. Higher temperatures can be used when pyrolysis of aerogels or xerogels that do not have a cathode material embedded. However, in the case of cathode materials such as lithium metal phosphate particles described herein, there is a risk that undesirable crystals may form in the LMP material as the temperature rises, which can lead to a decrease in electrochemical performance. However, according to this disclosure, the porous nature of the polymer network surrounding the LMP in the aggregate particles has been found to suppress these undesirable changes in the crystal structure. Therefore, according to this disclosure, carbonization can be carried out at temperatures of about 650°C to about 1000°C, or 650°C to about 800°C. Carbonization time may vary depending on the temperature used. For example, carbonization at approximately 800°C can take 5 to 10 hours, or even 8 hours. However, carbonization at lower or higher temperatures may require longer or shorter times, respectively, for the carbonization to proceed to its maximum extent (i.e., for all organic gel to be converted to carbon).

[0278] According to this disclosure, it is possible to adjust the amount of carbon in the final aggregate particles. For example, in some embodiments, it is desirable to prepare aggregate particles having a carbon percentage suitable for use in Li-ion batteries, where the amount of carbon is sufficient to provide the conductivity required for LMP without creating dead space / dead mass that is too high to hold charge in the final battery. Commercially available LFP-carbon materials may contain about 3% carbon and therefore about 97% LFP.

[0279] The carbon percentage in the aggregated particles can be calculated using the following formula:

number

[0280] For example, using 50 g of organogel precursor with a concentration of 0.05 g per gram of solution and a carbonization yield of 0.4, along with 10 g of LMP, yields aggregate particles with 9% C and 91% LMP. The above formula calculates only the carbon resulting from the carbonization of the polymer gel. Additional residual carbon from the LMP synthesis process may be present, which also contributes to the carbon in the aggregate particles. This is expected to be at most about 4%, and less than 1% (e.g., 0.5%).

[0281] H.Material properties Figures 5A and 5B illustrate the aggregated particles 500 according to this disclosure. As shown in Figure 5A, the particles 500 are substantially spherical and porous, and Figure 5A is a perspective view showing the visible pores 512 and 520 on the surface of the particles. It is also clear from Figure 5A that there are partially embedded LFP particles 508 that protrude to some extent within the core 504 of the particles 500.

[0282] Figure 5B is a cross-sectional view through the dotted line XX in Figure 5A, showing the same empty surface pores 520 and empty internal pores 516. Figure 5B also shows occupied internal pores 528 containing fully embedded LFP particles 532. Figure 5B also shows LFP particles 524 that are partially embedded and therefore protrude through the surface of the aggregated particle 500.

[0283] Overall, the aggregated particles of this disclosure are substantially spherical particles with a length of 50 m 2 If the amount exceeds / g, or 100m 2It has a high internal surface area that may exceed / g. The size of the beads may be 0.5-50 μm, 5-30 μm, or 1-10 μm. The pore size of the aggregated particles may be about 1-50 nm, for example, about 10-20 nm.

[0284] The aggregate particles (e.g., in the form of beads) contain cathode material particles (e.g., including LMP) at least partially embedded in a porous carbon matrix. In other words, some of the cathode material (e.g., LMP) particles are completely embedded within the matrix particles, while other cathode material (e.g., LMP) particles protrude from or above the surface of the matrix particles.

[0285] Cathode material (e.g., LMP) particles, at least partially embedded in a porous carbon matrix, are isolated from one another by the porous carbon network, meaning that while cathode material (e.g., LMP) particles may be in close proximity, they generally do not come into direct contact with each other (i.e., are not touching each other).

[0286] Figure 6 schematically shows an aggregated particle 600 according to the present disclosure, having a carbon network 604 surrounding LFP particles 608. Although Figure 6 is merely illustrative, it can be seen again that the LFP particles 608 are kept spaced apart by the carbon network 604, some LFP particles are completely embedded within particle 600, while others are partially embedded and visible on the surface of particle 600.

[0287] The carbon matrix may have a fibril structure, i.e., a structure containing the fibrils described above. A hierarchy of carbon fibrils may exist within the matrix. Figure 7 shows the carbon network 604 in more detail. As shown in Figure 7, the carbon network 704 branches into fibrils 712 on the surface of the LMP particle 708. In some embodiments, fibrils 721 in contact with the LFP surface may be thinner and have a higher density than fibrils not in contact with the LFP particle. While we do not wish to be bound by theory, it is conceivable that thinner, higher-density fibrils on the surface of the LMP particle would help coat the surface of the LFP particle and improve its conductivity.

[0288] Figures 8A–8D include four scanning electron microscope images of aggregated particles according to this disclosure. Figures 8A and 8B show aggregated particles with an LFP:carbon mass ratio of 75:25, while Figures 8C and 8D show aggregated particles with an LFP:carbon mass ratio of 90:10. The magnification is 10,000x for Figures 8A and 8C, and 50,000x for Figures 8B and 8D. Similar to the schematic diagrams in Figures 5A and 5B, the SEM images in Figures 8A–8D show substantially spherical aggregated particles with embedded LFP particles visible on the surface.

[0289] I. Electrochemical properties The aggregated particles of this disclosure surprisingly function as a very high-performance cathode material with fast ion and electron transfer velocities. This is at least in part due to the sufficient separation of the LFP particles in the conductive carbon matrix and the avoidance of undesirable LFP crystal growth during gel carbonization.

[0290] The starting LC-LFP material used in this disclosure may have a capacity of approximately 20 mAh / g. After grinding, this capacity may be slightly improved to approximately 80 mAh / g. The aggregated particles of this disclosure, including LFP particles, can achieve capacities exceeding 140 mAh / g, up to approximately 160 mAh / g.

[0291] As mentioned above, in existing conventional LFP materials, it is common to add a small amount of carbon to improve the conductivity of LFP materials with low conductivity. Since the addition of carbon corresponds to dead space, i.e., the mass of the battery cell that cannot hold charge, the amount of carbon needs to be kept to a minimum. Therefore, commercially available LFP-C materials may contain about 3% carbon. The aggregate particles of this disclosure, as mentioned above, can be manufactured with different amounts of carbon, such as 10% or less, 5% or less, or 3% or less, by changing the amount of carbon precursor (polymer) during manufacturing, with the remainder being LMP.

[0292] Experiments have shown that the aggregated particles of this disclosure can have a total capacity of approximately 130 mAh / g (normalized for the mass of LMP and carbon) at a charging rate of C / 20, even when containing a relatively large amount of carbon (e.g., 10%, see, for example, Figure 9 and the discussion below in this specification). This is close to the charging capacity of commercially available LFP-C when used as a test control. Furthermore, the aggregated particles of this disclosure have an improved first-cycle Coulomb efficiency (FCE) compared to the control sample.

[0293] In the case of aggregated particles according to this disclosure, as described above herein, reducing the carbon content reduces the dead mass, and therefore, it is expected that a higher capacity of 140 mAh / g or more, for example 150-160 mAh / g, can be achieved by having a lower carbon content.

[0294] The aggregated particles of this disclosure exhibit excellent capacity retention. When used as a cathode material, the aggregated particles retain capacity very well as the C rate increases, showing a capacity retention rate of over 80% at a C rate of 1C in a half-cell. In contrast, control LFP particles lose about 50% of their capacity at 1C, meaning their charge retention rate is only 50%.

[0295] The aggregated particles of this disclosure also exhibit extremely good cycle life. The material of the present invention shows no capacity loss whatsoever even after hundreds of charge cycles, whereas a product of the prior art is expected to lose approximately 75% of its initial capacity in direct comparison.

[0296] The aggregated particles of this disclosure demonstrate a further increase of over 50% in the actual capacity of LFP compared to simply crushed LFP, resulting in the achievement of capacities exceeding 145 mAh / g in LFP materials, even when starting from low-quality, low-performance, and inexpensive bulk LFP. A further unexpected advantage of the aggregated particles is their high-rate performance, with at least 80% capacity retention at 1C compared to C / 20. Thirdly, the materials of this disclosure exhibit excellent cycle life, with no capacity loss even after 300 cycles at a charge-discharge rate of 1C in a half-cell with a metallic lithium anode.

[0297] Experimental example Two examples of the synthesis of LFP / carbon aerogel materials according to this disclosure are described.

[0298] J.LC-LFP synthesis LC-LFP of 100 g of starting material was prepared as follows: 51.9 g of bulk iron oxide (Fe2O3) was stirred in 200 ml of water for 30 minutes. 74.94 g of phosphoric acid (85%) was added to this slurry and mixed for 30 minutes. Then, 25.22 g of Li2CO3 was added to the mixture in stages. The resulting slurry was mixed for a further 1 hour.

[0299] Separately, a polyamate salt solution was prepared by dissolving 1,4-phenylenediamine (PDA, 14.86 g) in 808 g of water, followed by the addition of triethylamine (TEA: 33.44 g, 46.09 mL, molar / molar ratio to PDA or PMDA 2.4:1) and PMDA (pyromellitic dianhydride 29.97 g, 0.138 mol, molar / molar ratio to PDA 1:1). 75.0 g of the resulting polyamate aqueous solution was added to the inorganic mixture (as a carbon source for Fe2O3 reduction) and mixed vigorously. The resulting slurry was heated to 130°C while mixing to remove water. After complete drying, the LFP precursor solid was pulverized into a fine powder and then heat-treated at 800°C for 8 hours under an inert gas. The resulting LFP exhibited a primary particle size in the range of 1 to 10 μm and a low specific volume of 20 mAh / g. Before using this LC-LFP in the LFP / carbon aerogel synthesis according to this disclosure, the particle size was reduced to less than 500 nm by ball milling for 10 hours. After ball milling, the specific capacity of the ground LFP improved to approximately 80 mAh / g.

[0300] II.LFMnP(Fe:Mn=2:1) ​​synthesis Step 1: Preparation of mixed oxide precursor. Ferrous sulfate (FeSO4.7H2O, 90.6g) and manganese sulfate (MnSO4.H2O, 27.5g) were dissolved in deionized water and mixed for 30 minutes. When this solution was added dropwise to an oxalic acid solution (90.0g in 500mL of H2O), a mixed metal oxalate, Fe, was formed. 2 / 3 Mn 1 / 3 C2O4.2H2O was immediately formed. After the addition was complete, the precipitate was filtered and washed multiple times with water. After drying, the solid was calcined in an air furnace at 350°C for 1 hour to produce powder, which was then oxidatively decomposed to produce the mixed oxide spinel MnFe2O4. Separately, an aqueous solution of polyamate salt was prepared by dissolving PDA (14.86 g) in 808 g of water, followed by the addition of triethylamine (TEA: 33.44 g, 46.09 mL, molar / molar ratio to PDA or PMDA 2.4:1) and PMDA (29.97 g, 0.0.138 mol, molar / molar ratio to PDA 1:1).

[0301] Step 2: Preparation of LFMnP. The mixed oxide obtained in Step 1 was ground into a fine powder and stirred in 200 mL of water for 30 minutes. Phosphoric acid (85%, 56.3 g) was added to this suspension and the mixture was mixed for 30 minutes. Next, Li2CO3 (19.0 g) was added to the mixture in stages, followed by 37.5 g of the above polyamate solution to the oxide inorganic mixture (as a carbon source for the reduction of iron trivalent), and the mixture was vigorously mixed. The resulting slurry was heated to 130°C while being mixed to remove the solvent (water). The dried mixed oxide precursor was ground into a fine powder and heated at 800°C for 8 hours under an inert gas.

[0302] III.LVP synthesis Bulk LVP was prepared as follows: Vanadium(V) oxide (V2O5, 29.6 g) was stirred in 100 mL of water for 30 minutes. Phosphoric acid (85%, 56.30 g) was added to this suspension, and the mixture was mixed for 30 minutes. Then, Li2CO3 (18.9 g) was added to the mixture in stages. The resulting slurry was mixed for 1 hour. Separately, a polyamate salt solution was prepared by dissolving PDA (14.86 g) in 808 g of water, followed by the addition of triethylamine (TEA: 33.44 g, 46.09 mL, molar / molar ratio 2.4:1 to PDA or PMDA) and PMDA (29.97 g, 0.138 mol, molar / molar ratio 1:1 to PDA). 75.0 g of the above polyamate solution was added to the inorganic mixture (as a carbon source for the reduction of V2O5), and the slurry was vigorously mixed. The solvent (water) was removed by heating to 130°C while mixing with a new slurry. The dried LVP precursor was pulverized into a fine powder and heated at 800°C for 8 hours under an inert gas.

[0303] IV. Aqueous preparation of LFP / micron-sized carbon aerogel beads at different weight ratios Micron-sized LFP / polyamic acid gel beads were prepared by gelling an aqueous solution of lithium salt of polyamic acid in an emulsion. The target density of the polyamic precursor solution was approximately 0.05 g / cm³. 3The solution was prepared by fixing the polyamic acid to a solution, dissolving 14.86 g of PDA in 808 g of water, then adding 12.13 g of lithium carbonate (molar ratio 1.2:1 to PDA or PMDA), and stirring the mixture for 5 to 15 minutes. 29.97 g of PMDA (0.138 mol, molar ratio 1:1 to PDA) was added to the mixture, and the mixture was stirred at room temperature for 24 to 48 hours. The resulting aqueous solution of polyamic acid carbonate had a viscosity of approximately 400 to 500 cP at room temperature.

[0304] Two different materials (with weight ratios of LFP / micron-sized carbon aerogel beads of 75 / 25 and 90 / 10) were prepared by the sol-gel method. The synthesis procedure began with dispersing pulverized LC-LFP in a pre-prepared polyamic precursor solution. The amount used was determined based on the carbon yield of the polyimide aerogel after carbonization (approximately 43%), the LFP carbon ratio, and the amount of LC-LFP used. For the nominal 75 / 25 ratio sample, 6 g of LC-LFP was mixed with 100 g of polyamic precursor solution, and for the nominal 90 / 10 ratio sample, 6 g of LC-LFP was mixed with 40 g of polyamic precursor solution.

[0305] The LC-LFP / polyamic precursor solution mixture was mixed for 5 minutes at 2500 rpm using a high-shear mixer in the presence of 2.5 mm zirconia beads (10 g of beads per 50 g of mixture) to ensure better dispersion of LFP in the polyamic precursor solution in the resulting slurry.

[0306] Acetic anhydride (3.21 g, 2.97 mL, molar / molar ratio of 4.3 to PMDA in polyamic acid for 75 / 25 material, or 1.28 g, 1.19 mL, molar / molar ratio of 4.3 to PMDA in polyamic acid for 90 / 10 material) was added to the obtained LFP / polyamic slurry and magnetically stirred for 60 seconds. At the end of this period, the precursor solution was poured into the immiscible phase under shear using a Loss mixer at 4000 rpm. The immiscible phase was prepared by dissolving 8.35 g of surfactant (Hypermer® H70) in 500 mL of mineral spirits. The precursor solution was added to the mineral spirit phase in a 1:4 v / v ratio. After stirring under high shear for 4-5 minutes, the mixture was removed from the Loss mixer and allowed to stand for 1-3 hours.

[0307] The low-density phase (mineral spirit solution) was decanted. The gel beads were recovered by vacuum filtration and the solvent was changed three times with ethanol. The ethanol-washed gel beads were dried using supercritical CO2, and these are called 75 / 25 and 90 / 10 LFP / PI aerogel beads.

[0308] To carbonize the aerogel materials, the two materials were heat-treated at 800°C for 8 hours under a nitrogen flow, using heating gradients and cooling rates of 5°C / min and 1°C / min, respectively.

[0309] Characteristics and performance of V.LFP / carbon aerogel Structural properties and texture properties The 75 / 25 and 90 / 10 materials (the figures in this specification refer to these ratios of LFP / carbon aerogel) each measured 126 m² when measured by the BET surface area analysis method. 2 / g and 58m 2 It showed a relatively high surface area of ​​ / g.

[0310] As shown in Figures 8A to 8D, SEM micrographs clearly show the sphericity of aggregate 75 / 25 materials with bead sizes ranging from 1 to 10 μm and well-dispersed LFP within the carbon aerogel framework. In the case of LFP / CA 90 / 10 materials, a lower amount of PI polymer results in incomplete inclusion of LFP aggregates, leading to a decrease in the sphericity of the microcomposite material. Nevertheless, well-separated LFP particles within the porous carbon aerogel are evident.

[0311] Electrochemical properties LFP-carbon aggregate particles were cast onto an Al foil current collector as a cathode and used as the cathode for a coin-cell sized half-cell. For comparison, coin-cell half-cells with commercially available LFP (purchased from Landt Instruments) cathodes were assembled under the same conditions and subjected to constant current charge-discharge cycles at various carbon rates.

[0312] Figure 9 shows the voltage profiles and first-cycle Coulomb efficiency (FCE) of three LFP-carbon aggregate particles. Clearly, commercially available LFP-C offers a maximum capacity of 150 mAh / g and an FCE slightly below 90%. Among the LFP-carbon aggregate particles, LFP-carbon aggregate particle 90:10 (LFP:carbon) shows a higher specific capacity of 130 mAh / g and an excellent FCE exceeding 96%. On the other hand, LFP-carbon aggregate particle 75:25 shows a lower specific capacity of less than 90 mAh / g and an FCE slightly above 90%. The lower specific capacity and FCE of the high-carbon variants of LFP-carbon aggregate particles are due to the higher carbon content, which contributes to dead mass, higher side reactions, and surface clogging.

[0313] Figure 10 shows the high-rate performance of the LFP-carbon aggregate particle cathode compared to commercially available LFPs. In both LFP-carbon aggregate particle electrodes, the capacity retention rate exceeds 80% as the C rate increases from C / 20 to 1C, whereas in commercially available LFPs, the capacity decreases by approximately 50%. Therefore, the LFP-carbon aggregate particles of this disclosure have superior high-rate performance.

[0314] Figure 11 shows the cycle lifetime of the LFP-carbon aggregate particle electrode at a 1C cycle rate and compares it to the cycle lifetime of a commercially available product. Clearly, the LFP-carbon aggregate particle electrode shows no capacity loss even after 300 cycles, while the commercially available sample lost approximately 75% of its initial capacity over the same period. This demonstrates the excellent cycle recovery capability of the product of this disclosure at high rates.

[0315] This application incorporates certain U.S. patents, U.S. patent applications, and other materials (e.g., papers) by reference. However, the text of such U.S. patents, U.S. patent applications, and other materials is incorporated by reference only to the extent that there is no conflict between such text and other descriptions and drawings contained herein. In the event of such a conflict, the conflicting text in the incorporated U.S. patents, U.S. patent applications, and other materials shall not be explicitly incorporated by reference into this Patent.

[0316] Further modifications and alternative embodiments of the present invention will become apparent to those skilled in the art upon consideration of this description. Therefore, this description should be interpreted as illustrative only and is intended to teach those skilled in the art general methods of carrying out the invention. It should be understood that the embodiments of the invention shown and described herein should be interpreted as examples of embodiments. Elements and materials may be replaced with those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be used independently, all of which will become apparent to those skilled in the art after benefiting from this description of the invention. Modifications to the elements described herein may be made without departing from the spirit and scope of the invention as set forth in the claims.

[0317] As used herein and in the claims, the terms “comprises” and “comprising,” and their variations, mean that a particular feature, process, or integer is included. This term should not be construed as excluding the presence of other features, processes, or components. The present invention includes, consists of, or essentially consists of the disclosed and claimed features.

[0318] The present invention may also be broadly comprised of any combination of parts, elements, processes, examples and / or features that are individually or collectively referred to or shown herein, as well as any combination of two or more such parts, elements, processes, examples and / or features. In particular, one or more features in any of the embodiments, examples and embodiments described herein may be combined with one or more features from any other embodiments, examples and embodiments described herein.

[0319] In combination with this disclosure, protection can be sought against any feature disclosed in any one or more public documents referenced herein.

[0320] While certain exemplary embodiments of the present invention have been described, the appended claims are not intended to be limited to these embodiments only. The claims should be interpreted literally, purposefully, and / or to encompass equivalents. Some embodiments of the present invention are shown below. [Embodiment 1] Matrix particles containing porous carbon, A plurality of cathode material particles, at least partially embedded within the matrix particles, Agglomerated particles containing these particles. [Embodiment 2] The aggregated particle according to Embodiment 1, wherein the plurality of cathode material particles include lithium metal phosphate (LMP) particles. [Embodiment 3] The aggregated particle according to Embodiment 2, wherein the metal (M) of the LMP is selected from the group consisting of Fe, Mn, V, and combinations of Fe and Mn. [Embodiment 4] The aggregated particles according to any one of Embodiments 1 to 3, wherein the matrix particles have a particle size of 100 nm to 20 microns, or 1 to 10 microns. [Embodiment 5] The aggregated particle according to any one of Embodiments 1 to 4, wherein at least a portion of the plurality of cathode material particles have an average particle size D50 of less than 250 nm. [Embodiment 6] The aggregated particle according to any one of Embodiments 1 to 5, wherein at least a portion of the plurality of cathode material particles have an average particle size D50 of less than 150 nm. [Embodiment 7] The internal specific surface area of ​​the matrix particles corresponding to the internal pores is 50 m². 2 / gram ~ 150ml 2 Agglomerated particles according to any one of Embodiments 1 to 6, which are / grams. [Embodiment 8] The aggregated particle according to Embodiment 7, wherein at least a portion of the internal specific surface area is configured to allow access for the electrolyte. [Embodiment 9] The aggregated particle according to any one of Embodiments 1 to 8, wherein the matrix particles include an aerogel or a xerogel. [Embodiment 10] The aggregated particles according to Embodiment 9, wherein the xerogel aerogel is formed as one or more beads or monoliths. [Embodiment 11] The aggregated particles according to Embodiment 9 or 10, wherein the aerogel or xerogel is derived from an organogel containing polyimide, polyamic acid, or a combination thereof. [Embodiment 12] The aggregated particles according to any one of Embodiments 9 to 11, wherein the aerogel or xerogel is a carbonized organogel. [Embodiment 13] The aggregated particle according to any one of embodiments 1 to 13, wherein the matrix particles have a pore structure including a fibril morphology. [Embodiment 14] The aggregated particle according to Embodiment 13, wherein the fibril morphology includes a support column of a carbonized material having a width in the range of about 2 to about 10 nm. [Embodiment 15] The aggregated particle according to any one of embodiments 1 to 14, wherein the matrix particles have a substantially uniform pore size distribution. [Embodiment 16] The aggregated particles according to any one of Embodiments 1 to 15, wherein the matrix particles have an average pore diameter of about 1 to about 50 nm, or about 5 to about 25 nm. [Embodiment 17] Agglomerated particles according to any one of embodiments 1 to 16, wherein the matrix particles include pores, and at least a portion of the pores are configured to accommodate the cathode material particles. [Embodiment 18] Agglomerated particles according to any one of Embodiments 1 to 17, wherein the weight ratio of carbon in the matrix material to the cathode material is less than 30:70, less than 10:90, or less than 5:95. [Embodiment 19] A method for preparing aggregated particles comprising porous carbon matrix particles and a plurality of cathode material particles at least partially embedded within the matrix particles, (a) Prepare an aqueous solution of a polyamic acid salt, (b) Mixing cathode material particles with an aqueous solution of the polyamic acid salt, (c1) Gelating the mixture from step (b) to form an organogel containing dispersed cathode material particles, and drying the organogel from step (c1) to form a dried intermediate, or (c2) Dry the mixture from step (b) to form a dried intermediate, (d) Carbonizing the dried intermediate to form the aggregate particles, The method, including the method described above. [Embodiment 20] The preparation of an aqueous solution of the aforementioned polyamic acid salt is Mixing a water-soluble diamine, a water-soluble carbonate or bicarbonate, and a tetracarboxylic dianhydride in water, The above components are reacted to obtain a solution of the polyamic acid salt, The method according to Embodiment 19, including the method described in Embodiment 19. [Embodiment 21] The aforementioned mixture Dissolving a water-soluble diamine in water to form an aqueous diamine solution, Adding the aforementioned water-soluble carbonate or bicarbonate to the diamine aqueous solution, Adding tetracarboxylic dianhydride to the aqueous solution of the diamine and the water-soluble carbonate or bicarbonate to form a solution, The aforementioned solution is stirred at a temperature in the range of approximately 4 to approximately 60°C for a period of approximately 1 hour to approximately 4 days. The method according to Embodiment 20, including the method described above. [Embodiment 22] The aforementioned mixture Dissolving a water-soluble diamine in water to form an aqueous diamine solution, Adding tetracarboxylic dianhydride to the aqueous solution of the diamine to form a suspension, The suspension is stirred at a temperature in the range of approximately 4 to approximately 60°C for a period of approximately 1 hour to approximately 4 days. Adding the aforementioned water-soluble carbonate or bicarbonate to the suspension, The suspension is stirred at a temperature in the range of approximately 4 to approximately 60°C for a period of approximately 1 hour to approximately 4 days to obtain an aqueous solution of the polyamic acid salt. The method according to Embodiment 20, including the method described above. [Embodiment 23] The aforementioned mixture The simultaneous or rapid and continuous addition of a water-soluble diamine, tetracarboxylic dianhydride, and a water-soluble carbonate or bicarbonate to water, The obtained mixture is stirred at a temperature in the range of approximately 4 to approximately 60°C for a period of approximately 1 hour to approximately 4 days to obtain an aqueous solution of the polyamic acid salt. The method according to Embodiment 20, including the method described above. [Embodiment 24] The method according to any one of Embodiments 20 to 23, wherein the water-soluble carbonate or bicarbonate comprises lithium, sodium, potassium, ammonium, or guanidinium cation. [Embodiment 25] The method according to any one of embodiments 20 to 24, wherein the water-soluble carbonate or bicarbonate is selected from the group consisting of lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, ammonium bicarbonate, guanidinium carbonate, and combinations thereof. [Embodiment 26] The water-soluble carbonate or bicarbonate is a carbonate, and the molar ratio of the water-soluble carbonate to the diamine is about 1 to about 1.4, or The water-soluble carbonate or bicarbonate is a bicarbonate, and the molar ratio of the water-soluble bicarbonate to the diamine is approximately 2 to approximately 2.8. The method according to any one of embodiments 20 to 25. [Embodiment 27] The method according to any one of Embodiments 20 to 26, wherein the molar ratio of the tetracarboxylic dianhydride to the diamine is about 0.9 to about 1.1. [Embodiment 28] The method according to any one of Embodiments 20 to 27, wherein the tetracarboxylic dianhydride is selected from the group consisting of biphthalic acid dianhydride (BPDA), benzophenone tetracarboxylic dianhydride (BTDA), oxydiphthalic acid dianhydride (ODPA), naphthalyl tetracarboxylic dianhydride, perylene tetracarboxylic dianhydride, and pyromellitic acid dianhydride (PMDA). [Embodiment 29] The method according to any one of embodiments 20 to 28, wherein the diamine is 1,3-phenylenediamine, 1,4-phenylenediamine, or a combination thereof. [Embodiment 30] The method according to any one of embodiments 20 to 29, wherein the diamine is 1,4-phenylenediamine. [Embodiment 31] The concentration range of the polyamic acid salt in the aqueous solution is approximately 0.01 to approximately 0.3 g / cm³ based on the weight of the polyamic acid. 3 The method according to any one of embodiments 20 to 30. [Embodiment 32] The organogel or intermediate is dried. Optionally, the organogel or intermediate may be washed or the solvent may be changed. The organogel or intermediate is exposed to high-temperature conditions to freeze-dry the organogel or intermediate, or the organogel or intermediate is brought into contact with supercritical fluid carbon dioxide. The method according to any one of embodiments 19 to 31, including the method described above. [Embodiment 33] The method according to any one of embodiments 19 to 32, wherein the porous carbon matrix comprises an aerogel or a xerogel. [Embodiment 34] The method according to any one of embodiments 19 to 33, wherein the carbonization is carried out in an inert atmosphere at a temperature of at least about 650°C. [Embodiment 35] The method according to any one of embodiments 19 to 34, wherein the cathode material particles comprise at least one lithium metallic phosphate (LMP), and the metal (M) is selected from iron, manganese, vanadium, and a combination of iron and manganese. [Embodiment 36] The method according to any one of embodiments 19 to 35, wherein the cathode material particles contain LiFePO4 or consist essentially of LiFePO4. [Embodiment 37] The method according to any one of embodiments 19 to 36, wherein the cathode material is pulverized before or during step (b). [Embodiment 38] The method according to Embodiment 37, wherein the grinding comprises grinding using a roller mill, planetary ball mill, or bead agitator mill, and optionally using at least one grinding medium selected from alumina, zirconia, and stainless steel. [Embodiment 39] The method according to Embodiment 37 or 38, wherein the grinding comprises dispersing the cathode material in a liquid phase optionally selected from water, ethanol, isopropanol, ethylene glycol, acetone, or a mixture thereof, and wet grinding the cathode material. [Embodiment 40] The method according to Embodiment 38 or Embodiment 39, wherein the grinding comprises dispersing the cathode material in an aqueous solution of the salt of the polyamic acid and wet grinding the cathode material during step (b) to obtain cathode material particles. [Embodiment 41] The method according to any one of embodiments 19 to 40, wherein step (b) includes mixing the cathode material in the aqueous solution for a period of time and under conditions sufficient to disperse it. [Embodiment 42] The method according to any one of embodiments 19 to 41, wherein the organogel contains polyimide, and the gelation in step (c1) includes adding a gelation initiator to convert the polyamic acid to the polyimide. [Embodiment 43] The method according to Embodiment 42, wherein the gelling initiator is acetic anhydride. [Embodiment 44] The method according to either embodiment 42 or 43, wherein the gelation of the mixture in step (c1) is carried out in a mold to form a wet gel monolith. [Embodiment 45] The method according to embodiment 44, further comprising crushing the wet gel monolith into a plurality of fragments before the drying. [Embodiment 46] (e) The method according to embodiment 50 or 51, further comprising grinding the dried material of step (c1). [Embodiment 47] The method according to Embodiment 46, wherein the grinding produces particles having an average particle size D50 of less than approximately 50 microns. [Embodiment 48] The method according to Embodiment 42, further comprising step (c1) adding the gelling initiator, and then mixing an aqueous solution of the polyamic acid salt with a non-aqueous miscible liquid to form an emulsion. [Embodiment 49] The method according to Embodiment 48, wherein the gelling initiator is acetic anhydride. [Embodiment 50] The method according to embodiment 48 or 49, wherein mixing for emulsion formation is performed for about 1 to about 30 minutes, or about 4 to about 15 minutes. [Embodiment 51] The method according to any one of embodiments 19 to 41, wherein the organogel contains a polyamic acid, and the gelation in step (c1) comprises adding a gelation initiator to convert the salt of the polyamic acid into the polyamic acid organogel, wherein the gelation initiator is an acid. [Embodiment 52] The method according to Embodiment 51, wherein the acid is a carboxylic acid. [Embodiment 53] The method according to Embodiment 52, wherein the carboxylic acid is acetic acid. [Embodiment 54] The method according to any one of embodiments 51 to 53, further comprising mixing the mixture of step (b) with a non-aqueous miscible liquid to form an emulsion between steps (b) and (c1). [Embodiment 55] The method according to embodiment 54, wherein the mixing is performed for a maximum of approximately 10 minutes, or for approximately 1 to 3 minutes. [Embodiment 56] The method according to embodiments 48-50 or 54-55, wherein the mixing is carried out using a homogenizer. [Embodiment 57] The method according to embodiment 56, wherein the homogenizer is operated at a speed of at least 1000 rpm, for example, about 1000 to about 9000 rpm. [Embodiment 58] The method according to any one of embodiments 48-50 or 54-57, wherein the non-aqueous miscible liquid is selected from the group consisting of mineral spirits, hexane, heptane, kerosene, octane, toluene, other hydrocarbons, and combinations thereof. [Embodiment 59] The method according to Embodiment 58, wherein the non-aqueous miscible liquid is a mineral spirit. [Embodiment 60] The method according to any one of embodiments 48-50 or 54-59, wherein the non-aqueous miscible liquid further comprises a surfactant dissolved therein. [Embodiment 61] The method according to Embodiment 60, wherein the surfactant is present in a concentration of about 1 to 2% by weight relative to the non-aqueous miscible liquid. [Embodiment 62] The method according to any one of embodiments 48 to 61, further comprising separating the beads of the organogel formed in step (c1) before drying. [Embodiment 63] The method according to embodiment 62, wherein the beads have an average size of 5 to 30 microns. [Embodiment 64] The method according to embodiment 62 or 63, wherein the separation comprises decanting the non-aqueous miscible liquid and optionally recycling the non-aqueous miscible liquid. [Embodiment 65] The method according to any one of embodiments 62 to 64, further comprising washing the gel beads with water, C1-C4 alcohols, acetone, acetonitrile, ether, tetrahydrofuran, toluene, liquid carbon dioxide, or a combination thereof. [Embodiment 66] The method according to any one of embodiments 19 to 65, wherein at least a portion of the plurality of cathode material particles have an average particle size D50 of less than 250 nm or less than 150 nm. [Embodiment 67] The method according to any one of embodiments 19 to 66, wherein the drying step (c2) is spray drying. [Embodiment 68] Aggregated particles comprising porous carbon matrix particles and a plurality of cathode material particles at least partially embedded within the matrix particles, which can be obtained by or by the method described in any one of embodiments 19 to 67. [Embodiment 69] The aggregated particle according to Embodiment 68, wherein the weight ratio of carbon in the matrix material to the cathode material is less than 30:70, less than 10:90, or less than 5:95. [Embodiment 70] An electrode containing aggregated particles as described in any one of Embodiments 1 to 18 or 68 to 69. [Embodiment 71] An energy storage device comprising aggregated particles as described in any one of Embodiments 1 to 18 or 68 to 69. [Embodiment 72] The energy storage device according to embodiment 71, wherein the energy storage device is a Li-ion battery.

Claims

1. Agglomerated particles, Matrix particles having a porous structure including fibril morphology, comprising an aerogel or xerogel, wherein the aerogel or xerogel is a carbonized organogel, the organogel comprises a polyimide, a polyamic acid, or a combination thereof, and the fibril morphology comprises aerogel or xerogel supports of the carbonized organogel having a width in the range of 2 to 10 nm, A plurality of cathode material particles at least partially embedded within the matrix particles, the plurality of cathode material particles comprising lithium metal phosphate (LMP) particles, Agglomerated particles containing these particles.

2. The aggregated particle according to claim 1, wherein the metal (M) of the LMP is selected from the group consisting of Fe, Mn, V, and combinations of Fe and Mn.

3. The aggregated particle according to claim 1, wherein the matrix particles have a particle size of 100 nm to 20 microns, or 1 to 10 microns.

4. The aggregated particle according to claim 1, wherein at least a portion of the plurality of cathode material particles have an average particle size D50 of less than 250 nm.

5. The aggregated particle according to claim 1, wherein at least a portion of the plurality of cathode material particles have an average particle size D50 of less than 150 nm.

6. The internal specific surface area of ​​the matrix particles corresponding to the internal pores is 50 m². ２ / gram ~ 150m ２ The aggregated particles according to claim 1, which are in the amount of / grams.

7. The aggregated particle according to claim 6, wherein at least a portion of the internal specific surface area is configured to allow access for the electrolyte.

8. The aggregated particles according to claim 1, wherein the aerogel or xerogel is formed as one or more beads or monoliths.

9. The aggregated particle according to claim 1, wherein the matrix particles have a substantially uniform pore size distribution.

10. The aggregated particle according to claim 1, wherein the matrix particles have an average pore diameter of 1 to 50 nm or 5 to 25 nm.

11. The aggregated particle according to claim 1, wherein the matrix particles include pores, and at least a portion of the pores are configured to accommodate the cathode material particles.

12. The aggregated particle according to claim 1, wherein the weight ratio of carbon in the matrix particles to the cathode material particles is less than 30:70, less than 10:90, or less than 5:

95.

13. A method for preparing aggregated particles according to claim 1, The aforementioned method, (a) Preparing an aqueous solution of a polyamic acid salt, comprising mixing a water-soluble diamine, a water-soluble carbonate or water-soluble bicarbonate, and a tetracarboxylic dianhydride in water, and reacting the water-soluble diamine, the water-soluble carbonate or water-soluble bicarbonate, and the tetracarboxylic dianhydride to obtain a solution of the polyamic acid salt, (b) Mixing cathode material particles with an aqueous solution of the polyamic acid salt, (c1) Gelating the mixture from step (b) to form an organogel containing dispersed cathode material particles, and drying the organogel from step (c1) to form a dried intermediate, or (c2) Dry the mixture from step (b) to form a dried intermediate, (d) Carbonizing the dried intermediate to form the aggregate particles, The method, including the method described above.

14. The aforementioned mixture Dissolving a water-soluble diamine in water to form an aqueous diamine solution, Adding the water-soluble carbonate or water-soluble bicarbonate to the aqueous diamine solution to form an aqueous solution of the water-soluble diamine and the water-soluble carbonate or water-soluble bicarbonate, Adding tetracarboxylic dianhydride to an aqueous solution of the water-soluble diamine and the water-soluble carbonate or water-soluble bicarbonate to form a solution, The aforementioned solution is stirred at a temperature in the range of 4 to 60°C for a period of 1 hour to 4 days. The method according to claim 13, including the method described in claim 13.

15. The aforementioned mixture Dissolving a water-soluble diamine in water to form an aqueous diamine solution, Adding tetracarboxylic dianhydride to the aqueous solution of the diamine to form a suspension, The suspension is stirred at a temperature in the range of 4 to 60°C for a period of 1 hour to 4 days. Adding the aforementioned water-soluble carbonate or water-soluble bicarbonate to the suspension, The suspension is stirred at a temperature in the range of 4 to 60°C for a period of 1 hour to 4 days to obtain an aqueous solution of the polyamic acid salt. The method according to claim 13, including the method described in claim 13.

16. The aforementioned mixture The simultaneous or rapid and continuous addition of a water-soluble diamine, tetracarboxylic dianhydride, and a water-soluble carbonate or water-soluble bicarbonate to water, The obtained mixture is stirred at a temperature in the range of 4 to 60°C for a period of 1 hour to 4 days to obtain an aqueous solution of the polyamic acid salt. The method according to claim 13, including the method described in claim 13.

17. The method according to claim 13, wherein the water-soluble carbonate or water-soluble bicarbonate comprises lithium, sodium, potassium, ammonium, or guanidinium cation.

18. The method according to claim 13, wherein the water-soluble carbonate or water-soluble bicarbonate is selected from the group consisting of lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, ammonium bicarbonate, guanidinium carbonate, and combinations thereof.

19. The water-soluble carbonate or water-soluble bicarbonate is a carbonate, and the molar ratio of the water-soluble carbonate to the diamine is 1 to 1.4, or The water-soluble carbonate or water-soluble bicarbonate is a bicarbonate, and the molar ratio of the water-soluble bicarbonate to the diamine is 2 to 2.

8. The method according to claim 13.

20. The method according to claim 13, wherein the molar ratio of the tetracarboxylic dianhydride to the diamine is 0.9 to 1.

1.

21. The method according to claim 13, wherein the tetracarboxylic dianhydride is selected from the group consisting of biphthalic acid dianhydride (BPDA), benzophenone tetracarboxylic dianhydride (BTDA), oxydiphthalic acid dianhydride (ODPA), naphthalyl tetracarboxylic dianhydride, perylene tetracarboxylic dianhydride, and pyromellitic acid dianhydride (PMDA).

22. The method according to claim 13, wherein the diamine is 1,3-phenylenediamine, 1,4-phenylenediamine, or a combination thereof.

23. The method according to claim 13, wherein the diamine is 1,4-phenylenediamine.

24. The concentration range of the polyamic acid salt in the aqueous solution is 0.01 to 0.3 g / cm³ based on the weight of the polyamic acid. ３ The method according to claim 13.

25. The organogel or intermediate is dried. Optionally, the organogel or intermediate may be washed or the solvent may be changed. The organogel or intermediate is exposed to high-temperature conditions to freeze-dry the organogel or intermediate, or the organogel or intermediate is brought into contact with supercritical fluid carbon dioxide. The method according to claim 13, including the method described in claim 13.

26. The method according to claim 13, wherein the carbonization is carried out in an inert atmosphere at a temperature of at least 650°C.

27. The cathode material particles are LiFePO ４ including or substantially LiFePO ４ The method according to claim 13, comprising:

28. The method according to claim 13, wherein the cathode material is pulverized before or during step (b).

29. The method according to claim 28, wherein the grinding comprises grinding using a roller mill, a planetary ball mill, or a bead agitator, and optionally using at least one grinding medium selected from alumina, zirconia, and stainless steel.

30. The method according to claim 28, wherein the grinding comprises dispersing the cathode material in a liquid phase optionally selected from water, ethanol, isopropanol, ethylene glycol, acetone, or a mixture thereof, and wet grinding the cathode material.

31. The method according to claim 29, wherein the pulverization comprises dispersing the cathode material in an aqueous solution of the salt of the polyamic acid, and wet pulverizing the cathode material during step (b) to obtain cathode material particles.

32. The method according to claim 13, wherein step (b) comprises mixing the cathode material in the aqueous solution for a period of time and under conditions sufficient to disperse it.

33. The method according to claim 13, wherein the organogel contains polyimide, and the gelation in step (c1) includes adding a gelation initiator to convert the polyamic acid to the polyimide.

34. The method according to claim 33, wherein the gelling initiator is acetic anhydride.

35. The method according to claim 33, wherein the gelation of the mixture in step (c1) is carried out in a mold to form a wet gel monolith.

36. The method according to claim 35, further comprising crushing the wet gel monolith into a plurality of fragments before the drying.

37. The method according to claim 35, further comprising (e) grinding the dried intermediate of step (c1).

38. The method according to claim 37, wherein the grinding produces particles having an average particle size D50 of less than 50 microns.

39. The method according to claim 33, further comprising step (c1) adding the gelling initiator, and then mixing an aqueous solution of the polyamic acid salt with a non-aqueous miscible liquid to form an emulsion.

40. The method according to claim 39, wherein the gelling initiator is acetic anhydride.

41. The method according to claim 39, wherein mixing for emulsion formation is carried out for 1 to 30 minutes or 4 to 15 minutes.

42. The method according to claim 13, wherein the organogel contains a polyamic acid, and the gelation in step (c1) comprises adding a gelation initiator to convert a salt of the polyamic acid into the polyamic acid organogel, wherein the gelation initiator is an acid.

43. The method according to claim 42, wherein the acid is a carboxylic acid.

44. The method according to claim 43, wherein the carboxylic acid is acetic acid.

45. The method according to claim 42, further comprising mixing the mixture of step (b) with a non-aqueous miscible liquid to form an emulsion between step (b) and (c1).

46. The method according to claim 45, wherein the mixing is performed for a maximum of 10 minutes or for 1 to 3 minutes.

47. The method according to claim 39, wherein the mixing is carried out using a homogenizer.

48. The method according to claim 47, wherein the homogenizer is operated at a speed of at least 1,000 rpm, for example, 1,000 to 9,000 rpm.

49. The method according to claim 39, wherein the non-aqueous miscible liquid is selected from the group consisting of mineral spirits, hexane, heptane, kerosene, octane, toluene, other hydrocarbons, and combinations thereof.

50. The method according to claim 49, wherein the non-aqueous miscible liquid is a mineral spirit.

51. The method according to claim 39, wherein the non-aqueous miscible liquid further comprises a surfactant dissolved therein.

52. The method according to claim 51, wherein the surfactant is present in a concentration of 1 to 2% by weight relative to the non-aqueous miscible liquid.

53. The method according to claim 39, further comprising separating the beads of the organogel formed in step (c1) before drying.

54. The method according to claim 53, wherein the beads have an average size of 5 to 30 microns.

55. The method according to claim 53, wherein the separation comprises decanting the non-aqueous miscible liquid and optionally recycling the non-aqueous miscible liquid.

56. The method according to claim 53, further comprising washing the beads with water, C1-C4 alcohols, acetone, acetonitrile, ether, tetrahydrofuran, toluene, liquid carbon dioxide, or a combination thereof.

57. The method according to claim 14, wherein at least a portion of the plurality of cathode material particles have an average particle size D50 of less than 250 nm or less than 150 nm.

58. The method according to claim 13, wherein the drying step (c2) is spray drying.

59. An electrode comprising aggregated particles as described in claim 1.

60. An energy storage device comprising aggregated particles as described in claim 1.

61. The energy storage device according to claim 60, wherein the energy storage device is a Li-ion battery.

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