Porous solids and methods of making porous solids

Abstract

The disclosure provides porous solids, devices and systems including such porous solids, and methods of preparing porous solids. The methods can include processing a mixture including particles and a powder, the particles including a first compound, the powder including a second compound different from the first compound, and the method including heating the mixture to form a porous solid including the second compound, where the heating sublimates at least a portion of the first compound.

Description

[0001] POROUS SOLIDS AND METHODS OF MAKING POROUS SOLIDS

[0002] Cross-Reference to Related Applications

[0003] This application claims the benefit of U.S. patent application 63 / 678,936, filed August 2, 2024, and entitled “Porous structures: Methods of Producing and Applications” and U.S. patent application 63 / 725,693, filed November 27, 2024, and entitled “Green preparation of porous electrodes containing Si via sublimation and regeneration of nanostructured terephthalic acid for enhanced Li-ion storage.” The entire disclosure of each of these applications is incorporated by reference herein.

[0004] Field

[0005] The disclosure provides porous solids, devices and systems including such porous solids, and methods of preparing porous solids. The methods can include processing a mixture including particles and a powder, the particles including a first compound, the powder including a second compound different from the first compound, and the method including heating the mixture to form a porous solid including the second compound, where the heating sublimates at least a portion of the first compound.

[0006] Background

[0007] Porous compositions can have advantages over non-porous compositions in various applications. For example, materials with porosity can have a greater surface area for physical and / or chemical interactions, pathways to facilitate the transport of species, and / or free spaces to accommodate volume changes, relative to materials without porosity.

[0008] Summary

[0009] The disclosure provides porous solids, devices and systems including such porous solids, and methods of preparing porous solids. The methods can include processing a mixture including particles and a powder, the particles including a first compound, the powder including a second compound different from the first compound, and the method including heating the mixture to form a porous solid including the second compound, where the heating sublimates at least a portion of the first compound.

[0010] The methods of the disclosure can be relatively simple, fast, inexpensive, and / or scalable relative to certain other methods for preparing porous compositions. For example, the methods of the disclosure can be performed with less expensive and / or less harmful reagents, shorter procedures, and / or fewer steps relative to certain other methods for preparing porous compositions. The methods of the disclosure can introduce porosity into materials, such as Si, faster, more easily, with greater scalability, and / or without the use of harmful chemicals relative to certain other methods for introducing porosity, such as through certain uses of a polymer such as PVA and / or by certain acid treatments of a silica-containing alloy. The methods of the disclosure can include the use of a compound, such as terephthalic acid (TP A), which can be recovered and reused, thereby potentially reducing costs and environmental impact.

[0011] The porous compositions of the disclosure can be used in various applications, such as catalysts, phase change materials, water desalination (e.g., water desalination media, electrodes for water desalination), biomaterials (e.g., biomaterials promoting osteoinductivity and / or bone regeneration), materials for separation, purification and / or conversion of gas species (e.g., CO2), adsorbents (e.g., for organic, inorganic, and / or radioactive materials), and electrode materials for energy storage devices such as supercapacitors and metal-ion batteries. The porous compositions of the disclosure can be used to prepare electrodes and electrode materials with relatively good performance, including for example, relatively good charge transfer, relatively good integrity, relatively good energy density, relatively good theoretical capacity, relatively low charge potential, relatively good conductivity, and / or relatively good porosity, relative to certain other electrodes and electrode materials, such as graphite and / or silicon materials without porosity. The electrodes can have relatively good resistance to pulverization from lithiation / delithiation, relative to certain other electrodes, such as silicon materials without porosity. Additionally, porous compositions of the disclosure can include relatively abundant materials such as silicon.

[0012] In a first aspect, the disclosure provides a method of processing a mixture including particles and a powder, the particles including a first compound, the powder including a second compound different from the first compound, the method including heating the mixture to form a porous solid including the second compound, wherein the heating sublimates at least a portion of the first compound.

[0013] In a second aspect, the disclosure provides a method of processing a mixture including particles and a powder, the particles including a first compound, the powder including a second compound different from the first compound, the method including heating the mixture to form a porous solid including the second compound, wherein the heating removes at least a portion of the first compound; and the first compound includes a member selected from the group consisting of: CXHY, where X and Y are a number from 1 to 16; CxHyOz, where X, Y and Z are a number from 1 to 16; and CXHYAZ, where A is a halogen and where X, Y and Z are a number from 1 to 16.

[0014] In some embodiments, the removing at least a portion of the first compound includes sublimating at least a portion of the first compound.

[0015] In some embodiments, the method further includes mixing the particles of the first compound and the powder of the second compound to form the mixture. In some embodiment, mixing the particles of the first compound and the powder of the second compound includes mechanically pressing the mixture.

[0016] In some embodiments, the mixture includes from 0.01 wt. % to 99.9 wt. % of the first compound. In some embodiments, the mixture includes from 1 wt. % to 80 wt. % of the first compound. In some embodiments, the mixture includes from 2 wt. % to 50 wt. % of the first compound. In some embodiments, the mixture includes from 5 wt. % to 30 wt. % of the first compound.

[0017] In some embodiments, the mixture includes from 0.1 wt. % to 99.9 wt. % of the second compound. In some embodiments, the mixture includes from 10 wt. % to 99 wt. % of the second compound. In some embodiments, the mixture includes from 30 wt. % to 99 wt. % of the second compound. In some embodiments, the mixture includes from 80 wt. % to 99 wt. % of the second compound.

[0018] In some embodiments, the mixture is a powder.

[0019] In some embodiments, the mixture is a slurry.

[0020] In some embodiments, the mixture is heated to a temperature of from 70 °C to 500 °C to form the porous solid. In some embodiments, the mixture is heated to a temperature of from 150 °C to 400 °C to form the porous solid. In some embodiments, the mixture is heated to a temperature of from 200 °C to 400 °C to form the porous solid. In some embodiments, the mixture is heated to a temperature of from 300 °C to 400 °C to form the porous solid.

[0021] In some embodiments, the mixture is heated at a pressure of from 1 mbar to 2026.5 mbar (2 atm) to form the porous solid. In some embodiments, the mixture is heated at a pressure of from 1 mbar to 1013.25 mbar (1 atm), to form the porous solid.

[0022] In some embodiments, the mixture is heated for 1 second to 1 month to form the porous solid. In some embodiments, the mixture is heated for 10 seconds to 10 hours to form the porous solid. In some embodiments, the mixture is heated for 10 minutes to 5 hours to form the porous solid. In some embodiments, the mixture is heated for 10 minutes to 2 hours to form the porous solid.

[0023] In some embodiments, the mixture is heated under an inert atmosphere to form the porous solid.

[0024] In some embodiments, the mixture is heated under an atmosphere including at least one member selected from the group consisting of air, oxygen, hydrogen, argon, helium, and nitrogen to form the porous solid.

[0025] In some embodiments, the mixture is heated under an atmosphere including at least one gas selected from the group consisting of oxygen, hydrogen, argon, helium, and nitrogen to form the porous solid.

[0026] In some embodiments, the mixture is heated under an atmosphere including from 0 vol. % to 22 vol. % oxygen to form the porous solid. In some embodiments, the mixture is heated under an atmosphere including from 0 vol. % to 10 vol. % oxygen to form the porous solid. In some embodiments, the mixture is heated under an atmosphere including from 0 vol. % to 5 vol. % oxygen to form the porous solid. In some embodiments, the mixture is heated under an atmosphere including from 0 vol. % to 0.1 vol. % oxygen to form the porous solid.

[0027] In a third aspect, the disclosure provides a method of processing a mixture including a first compound and a second compound different from the first compound, the method including reducing a pressure around the mixture to form a porous solid including the second compound, wherein reducing the pressure sublimates at least a portion of the first compound.

[0028] In some embodiments, the mixture further includes a solvent and reducing the pressure sublimates at least a portion of the solvent.

[0029] In some embodiments, the mixture further includes a solvent and prior to reducing the pressure, a heat treatment is used to remove at least a portion of the solvent.

[0030] In some embodiments, the pressure is reduced to 100 mbar or less.

[0031] In some embodiments, reducing the pressure includes applying a vacuum to the mixture.

[0032] In some embodiments, the first compound includes CXHY, where X and Y are a number from 1 to 16, optionally where X and Y are a number from 1 to 10, optionally where X is a number from 7 to 14, and / or optionally where Y is a number from 4 to 16. In some embodiments, the first compound includes CxHyOz, where X, Y and Z are a number from 1 to 16, optionally where X, Y and Z are a number from 1 to 10, optionally where X is a number from 7 to 14, optionally where Y is a number from 4 to 16, and / or optionally where Z is a number from 1 to 4. In some embodiments, the first compound includes CxHyAz, where A is a halogen, optionally where A is Cl, and where X, Y and Z are a number from 1 to 16, optionally where X, Y and Z are a number from 1 to 10, optionally where X is a number from 7 to 14, optionally where Y is a number from 4 to 16, optionally where Z is a number from 1 to 4, and / or optionally where Z is a number from 1 to 2.

[0033] In some embodiments, the first compound includes at least one member selected from the group consisting of naphthalene, anthracene, benzoic acid, camphor, phthalic anhydride, para-dichlorobenzene and terephthalic acid.

[0034] In some embodiments, the first compound includes CsHeC .

[0035] In some embodiments, the first compound includes terephthalic acid.

[0036] In some embodiments, at atmospheric pressure, the first compound has a sublimation temperature of from 70 °C to 500 °C, optionally a sublimation temperature of from 200 °C to 500 °C, optionally a sublimation temperature of from 200 °C to 400 °C, or optionally a sublimation temperature of from 300 °C to 400 °C.

[0037] In some embodiments, the particles have a size of from 1 nm to 10 pm, optionally from 1 nm to 1 pm, optionally from 1 nm to 500 nm, or optionally from 1 nm to 100 nm.

[0038] In some embodiments, the particles have a largest linear dimension of from 1 nm to 10 pm, optionally from 1 pm to 1 mm, optionally from 1 pm to 200 pm, or optionally from 1 pm to 100 pm, from 100 nm to 10 pm, optionally from 500 nm to 10 pm, optionally from 100 nm to 1 pm, or optionally from 500 nm to 1 pm.

[0039] In some embodiments, the mixture further includes a metal-containing species. In some embodiments, the porous solid includes an oxide of the metal -containing species. In some embodiments, the metal-containing species includes at least one member selected from the group consisting of a tin-containing species and a zinc-containing species. In some embodiments, the metal-containing species includes at least one member selected from the group consisting of tin chloride (SnCh) and tin oxide (SnCh). In some embodiments, the mixture includes from 0.1 wt. % to 90 wt. % of the metal -containing species, optionally from 0.1 wt. % to 50 wt. % of the metal-containing species, or optionally from 0.1 wt. % to 20 wt. % of the metal-containing species. In some embodiments, the metal-containing species includes a tin-containing species and the porous solid includes particles including tin oxide. In some embodiments, the metal-containing species includes a zinc-containing species and the porous solid includes particles including zinc oxide. In some embodiments, heating the mixture forms a nanocrystalline metal oxide of the metal-containing species in the porous solid. In some embodiments, the porous solid includes a nanocrystalline metal oxide of the metal-containing species. In some embodiments, the nanocrystalline metal oxide have a particle size of from 1 nm to 50 nm, optionally from 1 nm to 10 nm, optionally from 2 nm to 20 nm, or optionally from 3 nm to 10 nm.

[0040] In some embodiments, the second compound includes at least one member selected from the group consisting of a polymer, a metal, a metal oxide, a semimetal, a ceramic, a monomer capable of polymerizing to form a polymer, graphite, glassy carbon, and a zinc- containing metal-organic framework.

[0041] In some embodiments, the second compound includes at least one member selected from the group consisting of a metal, a metal oxide, a semimetal, and a ceramic, and heating the mixture sinters the second compound.

[0042] In some embodiments, the second compound includes a polymer, and heating the mixture crosslinks the polymer.

[0043] In some embodiments, the second compound includes at least one polymer selected from the group consisting of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene (SBR), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), a polyurethane (PU), an acrylic-based polymer, and a polyimide (PI).

[0044] In some embodiments, the second compound includes a polymer, and the mixture further includes a crosslinking agent.

[0045] In some embodiments, the second compound includes a member selected from the group consisting of silicon and a silicon oxide.

[0046] In some embodiments, the second compound includes a member selected from the group consisting of alumina, zirconia, calcium apatite, and a high entropy oxide.

[0047] In some embodiments, the second compound includes a member selected from the group consisting of LiFePCh, LiMnFePCU, LiCoCh, LiM CU, LiNiMnCoCh, LiNiCoAlCh, NaFePCU, and NaMnCh.

[0048] In some embodiments, the second compound includes a polyimide and silicon.

[0049] In some embodiments, the mixture includes a solvent. In some embodiments, the solvent includes a solvent selected from the group consisting of water and NMP

[0050] In some embodiments, the mixture is coated onto a substrate and dried to remove the solvent. In some embodiments, the substrate includes a member selected from the group consisting of a copper substrate, an aluminium substrate, and a carbon substrate. In some embodiments, the porous solid includes an average pore diameter of from 1 nm to 50 nm, optionally from 2 nm to 40 nm, or optionally from 10 nm to 30 nm.

[0051] In some embodiments, the porous solid is microporous.

[0052] In some embodiments, the porous solid is mesoporous.

[0053] In some embodiments, the porous solid includes a pore volume of from 0.05 cm3 / g to 0.5 cm3 / g, optionally from 0.7 cm3 / g to 0.4 cm3 / g, optionally from 0.06 cm3 / g to 0.4 cm3 / g, or optionally from 0.1 cm3 / g to 0.3 cm3 / g.

[0054] In some embodiments, the method further includes condensing the sublimated first compound.

[0055] In some embodiments, the first compound includes terephalic acid, the particles have a size of from 1 nm to 100 nm, and the second compound includes a polyimide and Si.

[0056] In some embodiments, the method further includes manufacturing an electrode including the porous solid.

[0057] In some embodiments, the electrode is an anode.

[0058] In some embodiments, the electrode is a cathode.

[0059] In some embodiments, the method further includes making a battery including the electrode. In some embodiments, the battery includes a member selected from the group consisting of a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, and an aluminium-ion battery.

[0060] In some embodiments, the electrode has a Li-ion storage capacity of from 1000-3000 mAh / g, optionally from 1500-2800 mAh / g, or optionally from 1800-2500 mAh / g after 120 Li-ion insertion and extraction cycles at a current density of 200 mA / g.

[0061] In some embodiments, a full cell including the electrode and a second electrode including LiFePCU (LFP) having a discharge capacity of 150.6 mAh / g based on a mass of active materials at an anode and a cathode after 50 cycles with capacity retention rate of 97.8% has an average coulombic efficiency of at least 85 %, optionally at least 90 %, optionally at least 92 %, optionally at least 95 %, optionally at least 99 %, and / or optionally at most 100 %, optionally at most 99.9 %, at a current density of 800 mA / g.

[0062] In some embodiments, a full cell including the electrode and a second electrode including LiFePCU (LFP) includes a gravimetric energy density of from 350 Wh / kg to 600 Wh / kg.

[0063] In some embodiments, the first compound includes terephalic acid, the particles have a size of from 1 nm to 100 nm, the second compound includes a polyimide and Si, and the electrode includes a Li-ion storage capacity of at least 2355mAh / g after 120 Li-ion insertion and extraction cycles at a current density of 200 mA / g.

[0064] In some embodiments, a Li-ion diffusion value of the electrode during a second-cycle lithiation process, in a haff cell configuration at room temperature and a current density of 200 mA / g, is in a range of 10'10 0- 10'13 5cm2 / s, optionally in a of range 10'10 0- 10'12 0cm2 / s. In some embodiments, the minimum Li-ion diffusion value of the electrode during a second- cycle delithiation process, in a half-cell configuration at room temperature and a current density of 200 mA / g, is 4 to 10 times higher than the minimum Li-ion diffusion value of an electrode fabricated without the addition of terephalic acid under the same conditions, optionally 30 to 40 times higher than that of an electrode fabricated without the addition of terephalic acid under the same conditions.

[0065] In some embodiments, a full cell including the electrode and a second electrode, the second electrode including LiFePCU (LFP), includes a gravimetric energy density of from 350 Wh / kg to 600 Wh / kg. In some embodiments, a second-cycle galvanostatic charge profile of the full cell initially exhibits a sloping line within a potential range of 3.20 to 3.50 V, followed by a plateau at 3.5 ± 0.1 V. In some embodiments, a second-cycle galvanostatic discharge profile of the full cell initially exhibits a plateau at 3.5 ± 0.1 V, followed by a sloping line within the potential range of 2.90 to 3.30 V.

[0066] In a fourth aspect, the disclosure provides a composition including a polymer stable at a temperature of at least 200 °C and a compound selected from a metal, a metal oxide, a semimetal, and a ceramic, wherein the composition is porous.

[0067] In some embodiments, the polymer is stable at a temperature of at least 250 °C, optionally at least 300 °C, optionally at least 350 °C, optionally at least 400 °C, optionally at least 450 °C, optionally at least 500 °C, optionally at least 550 °C, and / or optionally at most 600 °C.

[0068] In some embodiments, the polymer includes one or more polymers selected from the group consisting of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene (SBR), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), a polyurethane (PU), an acrylic-based polymer, and a polyimide (PI).

[0069] In some embodiments, the polymer includes a polyimide. In some embodiments, the polyimide includes a thermosetting polyimide. In some embodiments, the polyimide includes a member selected from the group consisting of an aromatic polyimide, a semi -aromatic polyimide, and an aliphatic polyimide. In some embodiments, the compound includes a member selected from the group consisting of Si, SiO, SiCh, Fe2O3, FeO, FesC , P, SiP, SiP2, and SisP In some embodiments, the member includes particles with particle sizes of 1 nm to 5 pm, optionally with particle sizes of 5 nm to 1 pm, or optionally with particle sizes of 10 nm to 200 nm.

[0070] In some embodiments, the compound includes a member selected from the group consisting of semi-amorphous carbon, graphitic semi -spherical carbon particles, graphitic graphene nanosheets, and graphite powder.

[0071] In some embodiments, the compound includes a member selected from the group consisting of LiFePCh, LiMnFePC , LiCoCh, LiMmC , LiNiMnCoCh, LiNiCoAlCh, NaFePC and NaMnCh.

[0072] In some embodiments, the composition further includes metal oxide particles. In some embodiments, the metal oxide particles include a member selected from the group consisting of tin oxide and zinc oxide. In some embodiments, the metal oxide particles are nanocrystalline.

[0073] In some embodiments, the composition includes an average pore diameter of from 0.1 nm to 50 nm, optionally from 1 nm to 50 nm, optionally from 2 nm to 50 nm, optionally from 2 nm to 40 nm, or optionally from 10 nm to 30 nm.

[0074] In some embodiments, the composition is microporous.

[0075] In some embodiments, the composition is mesoporous.

[0076] In some embodiments, the composition includes a pore volume of from 0.05 cm3 / g to 0.5 cm3 / g, optionally from 0.7 cm3 / g to 0.4 cm3 / g, optionally from 0.06 cm3 / g to 0.4 cm3 / g, or optionally from 0.1 cm3 / g to 0.3 cm3 / g.

[0077] In a fifth aspect, the disclosure provides an electrode including a composition of the disclosure.

[0078] In some embodiments, the electrode is an anode.

[0079] In some embodiments, the electrode is a cathode.

[0080] In a sixth aspect, the disclosure provides a battery, including an electrode of the disclosure.

[0081] Brief Description of the Figures

[0082] Figure 1 shows a schematic for a method of forming a porous solid.

[0083] Figure 2a shows a schematic for a method of forming an electrode.

[0084] Figure 2b schematically depicts an embodiment of a cell of a battery. Figure 3a shows, from top to bottom. X-ray diffraction (XRD) patterns of micro-TPA, nano-TPA, and TPA.

[0085] Figure 3b shows a graph of thermogravimetric (TG) thermograms of micro-TPA and nano-TPA.

[0086] Figures 3c and 3d show scanning electron microscopy (SEM) micrographs of micro- TPA and nano-TPA, respectively.

[0087] Figure 3e shows a high-resolution transmission electron microscopy (TEM) micrograph of nano-TPA.

[0088] Figure 3f shows a fast Fourier transform (FFT) pattern recorded on a SnCh nanoparticle on nano-TPA.

[0089] Figures 3g-3i show X-ray photoelectron spectroscopy (XPS) measurements of nano- TPA.

[0090] Figure 3j shows a bright field TEM micrograph of nano-TPA.

[0091] Figure 3k shows an electron diffraction pattern of nano-TPA.

[0092] Figure 31 shows a high magnification TEM micrograph recorded on a SnCh nanocrystal.

[0093] Figure 3m shows a FFT pattern recorded on a SnCh nanocrystal.

[0094] Figure 3n shows an energy dispersive spectroscopy (EDS) mapping analysis showing the elemental distribution of C, O, and Sn.

[0095] Figures 3o and 3p show XRD patterns.

[0096] Figure 4a shows XRD patterns of a mixture of polyimide (PI) with nano-TPA (second from bottom), and the mixture after heating at 250°C (second from top) and 350 °C (top). The XRD patterns for TPA and SnCh are included at the bottom for comparison.

[0097] Figure 4b shows an XRD pattern of the deposit obtained from condensation of sublimated TPA at 350 °C. The inset shows the SEM micrograph of the sample. The XRD pattern for TPA is included at the bottom for comparison.

[0098] Figure 4c shows XRD patterns of a mixture of PI with micro-TPA (second from bottom), and the mixture after heating at 250°C (second from top) and 350 °C (top). The XRD pattern for TPA is included at the bottom for comparison.

[0099] Figures 5a, 5c, and 5e show lS adsorption-desorption isotherms of the samples Si@PI@350, Si@PI@nano-TPA@350, and Si@PI@micro-TPA@350, respectively.

[0100] Figures 5b, 5d, and 5f show the pore size distribution of the samples Si@PI@350, Si@PI@nano-TPA@350, and Si@PI@micro-TPA@350, respectively. Figure 5g shows thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) thermograms of PI@nano-TP A.

[0101] Figures 5h and 5i show thermogravimetric-differential scanning calorimetry (TG- DSC) thermograms of PI@nano-TPA@350 powder and PI powder, respectively.

[0102] Figures 6a-6c show C Is, N Is, and O ls XPS spectra, respectively, of PI@nano- TPA.

[0103] Figures 6d-6f show C Is, N Is, and O ls XPS spectra, respectively, of PI@nano- TPA@350.

[0104] Figures 6g-6j show Fourier transform infrared (FTIR) spectra of nano-TPA, PI, PI@nano-TPA, and PI@nano-TPA@350, respectively.

[0105] Figures 6k-6o show FTIR spectra of TPA, PI, PI@nano-TPA, PI@nano-TPA@250, and PI@nano-TPA@350, respectively.

[0106] Figures 6p and 6q show TEM micrographs.

[0107] Figures 7a shows initial charge-discharge curves of electrodes with different binders.

[0108] Figures 7b and 7c show charge-discharge curves and CV curves (0.1 mV / s), respectively, of Si@PI@nano-TPA@E-350 electrodes.

[0109] Figures 7d and 7e show the Li-ion storage cycle performance of various electrodes as described in Table 1, in terms of specific capacity and coulombic efficiency (CE), respectively, at the current density of 200 mA / g.

[0110] Figure 7f shows the rate performance of various electrodes at different values of current density.

[0111] Figures 7g and 7h show the cycling performance in terms of specific capacity coulombic efficiency (CE), respectively, of various electrodes at 800 mA / g.

[0112] Figure 7i shows the performance of Si@PI@nano-TPA@E-350 in comparison with electrodes reported in the literature.

[0113] Figures 7j and 7k show graphs of the Li+storage cycle performances, in terms of specific capacity and coulombic efficiency, respectively, of Si@PI-350 electrodes with different mass ratios of the components (Si: PI: TPA: Super P = 5:2:2:1, 6: 1 : 1 :2, 4:2:2:2, and 6:2:0:2) and Si@CMC at 200 mA g’1.

[0114] Figures 8a and 8b show the Li+storage cycling performances, in terms of specific capacity (left axis) and coulombic efficiency (right axis), of Si@PI@nano-TPA@E-350 electrode at 5000 mA / g and 10000 mA / g, respectively.

[0115] Figure 9a shows Nyquist plots of various electrodes. Figure 9b shows galvanostatic intermitent titration technique (GITT) curves for Si@PI@E-350 and Si@PI@nano-TPA@E-350 recorded at room temperature during the second discharge / charge cycle.

[0116] Figure 9c shows calculated values of diffusion coefficient of Li+into / out of the elecrodes (DLI+).

[0117] Figure 9d shows charge and discharge curves of a lithium iron phosphate (LFP) cathode and Si@PI@nano-TPA@E-350 anode in half-cell at 200 mA / g.

[0118] Figures 9e and 9f show charge and discharge curves and full-cell cycling performance, respectively, of a LFP / / Si@PI@nano-TPA@E-350 full-cell at 200 mA / g, based on the combined masses of the active materials at the anode and the cathode.

[0119] Figure 9g shows a schematic for a simulated circuit used to calculate the impedance of electrodes.

[0120] Figure 9h shows a graph of the second cycle galvanostatic charge / discharge (GCD) profiles of the half cells (LFP cathode and the Si@PI@nano-TPA@E-350 anode) and the full cell (LFP / / Si@PI@nano-TPA@E-350) at 200 mA / g.

[0121] Figure 10a shows a SEM micrograph of a pristine Si@PI@E-350 electrode.

[0122] Figure 10b shows a SEM micrograph of a Si@PI@E-350 electrode after 130 cycles.

[0123] Figure 10c shows a SEM micrograph of a pristine Si@PI@nano-TPA@E-350 electrode.

[0124] Figure lOd shows a SEM micrograph of a Si@PI@nano-TPA@E-350 electrode after 130 cycles.

[0125] Detailed Description

[0126] Porous solids and methods of making porous solids

[0127] Figure 1 shows a schematic for a method 1000 of forming a porous solid 1400 having pores 1450. Particles 1100 and powder 1200 are mixed to form a mixture 1300 including the powder 1200 and the particles 1100. The particles 1100 includes a first compound, and the powder 1200 includes a second compound which is different from the first compound. The mixture 1300 is heated which causes the first compound to be removed (e.g., sublimated) and the second compound to form the porous solid 1400 with the pores 1450. The removed (e.g., sublimated) first compound can be condensed to form a solid 1150 of the first compound. Without wishing to be bound by theory, it is believed that the removal (e.g., sublimation) of the particles 1100 of the first compound creates the porosity in the porous solid 1400 where the particles 1100 of the first compound were present before removal (e.g., sublimation).

[0128] In general, removing the first compound includes sublimating the first compound and the first compound can be any appropriate compound with an appropriate sublimation temperature. In some embodiments, in addition to or in alternative to sublimating the first compound, the first compound can be removed by one or more additional methods, such as melting, optionally followed by evaporation.

[0129] In some embodiments, the first compound is of formula CXHY, where X and Y are each a number from 1 to 16. In some embodiments, X and Y are each a number from 1 to 10. In some embodiments, X is a number from 7 to 14. In some embodiments, Y is a number from 4 to 16.

[0130] In some embodiments, the first compound is of formula CxHyOz, where X, Y and Z are each a number from 1 to 16. In some embodiments, X, Y and Z are each a number from 1 to 10. In some embodiments, X is a number from 7 to 14. In some embodiments, Y is a number from 4 to 16. In some embodiments, Z is a number from 1 to 4.

[0131] In some embodiments, the first compound is of formula CxHyAz, where A is a halogen (e.g., Cl) and X, Y and Z are each a number from 1 to 16. In some embodiments, X, Y and Z are each a number from 1 to 10. In some embodiments, X is a number from 7 to 14. In some embodiments, Y is a number from 4 to 16. In some embodiments, Z is a number from 1 to 2.

[0132] In some embodiments, the first compound has a chemical composition of CsHeC . In some embodiments, the first compound is TPA, which has a sublimation temperature in the range of 300 °C to 350 °C. Without wishing to be bound by theory, it is believed that the sublimation temperature can be impacted by a range of factors, such as the heating rate and pressure. It is further believed that depending on conditions, the sublimation temperature of TPA can be in the range of 250 °C to 450 °C. In addition to or in alternative to TPA, the first compound can include naphthalene (CioHs, sublimation point of around 80°C), anthracene (C14H10, sublimation point of around 190°C), benzoic acid (C7H6O2, sublimation point of around 100°C), camphor (CioHieO, sublimation point of 175°C), phthalic anhydride (CsF O3, sublimation point of around 131°C), and / or para-dichlorobenzene (CeFUCh, sublimation point of around 173°C). These sublimation temperatures are at atmospheric pressure. It is to be noted that altering the pressure can influence the sublimation temperature (see discussion below) of a given compound. In some embodiments, the first compound has a sublimation temperature of at least 200 (e.g., at least 210, at least 220, at least 230, at least 240, at least 250, at least 260, at least 270, at least 280, at least 290, at least 300, at least 310, at least 320, at least 330, at least 340, at least 350, at least 360, at least 370, at least 380, at least 390) °C and / or at most 400 (e.g., at most 390, at most 380, at most 370, at most 360, at most 350, at most 340, at most 330, at most 320, at most 310, at most 300, at most 290, at most 280, at most 270, at most 260, at most 250, at most 240, at most 230, at most 220, at most 210) °C at atmospheric pressure.

[0133] In general, the particles 1100 can have any appropriate size. In some embodiments, the particles have a largest linear dimension (e.g., diameter) of at least 1 nm (e.g., at least 2 nm, at least 5 nm, at least 10 nm, at least 20 nm, at least 50 nm, at least 100 nm, at least 200 nm, at least 500 nm, at least 1 pm, at least 2 pm, at least 5 pm) and / or at most 10 pm (e.g., at least 5 pm, at least 2 pm, at least 1 pm, at least 500 nm, at least 200 nm, at least 100 nm, at least 50 nm, at least 20 nm, at least 10 nm, at least 5 nm, at least 2 nm). In some embodiments, the first compound is nanostructured (includes at least one dimension below 100 nm).

[0134] Although the method 1000 includes particles 1100 including a first compound, particles 1100 including a third compound can also be used. In some embodiments, the particles 1100 include the first compound and the third compound. In some embodiments, the mixture 1300 includes particles 1100 that include the first compound and particles 1100 that include the third compound. Like the first compound, the third compound is removed (e.g., sublimated) when the mixture 1300 is heated to form the porous solid 1400. Without wishing to be bound by theory, it is believed that the removal (e.g., sublimation) of the particles 1100 of the third compound create the porosity in the porous solid 1400 where the particles 1100 of the third compound were present before removal (e.g., sublimation). For example, in some embodiments, the first compound is anthracene and the third compound is terephthalic acid, the anthracene will sublimate at a temperature of 160-210 °C and the terephthalic acid will sublimate at a temperature of 300-350 °C. Like the first compound, the third compound can be condensed to form a solid of the third compound.

[0135] In some embodiments, the particles 1100 and / or the first compound includes a composition disclosed in WO2023222880, the entire disclosure of which is incorporated by reference herein.

[0136] In general, the second compound can be any appropriate compound. For example, the second compound can include a metal, a metal oxide, a semimetal, a ceramic (e.g., AI2O3), a semi-conductor material, a polymer, a monomer capable of polymerizing to form a polymer, graphite, glassy carbon, a zinc-containing metal-organic framework (Zn-MOF) and / or a composite structure. In some embodiments, the second compound is selected based on the intended application and / or desired property for the porous solid 1400.

[0137] Examples of the metal include iron and aluminium. Without wishing to be bound by theory, it is believed that the inclusion of a metal can enhance the mechanical strength and / or conductivity of the porous solid 1400.

[0138] Without wishing to be bound by theory, it is believed that the inclusion of a ceramic (e.g., AI2O3) can enhance the thermal stability, chemical resistance, and / or hardness of the porous solid 1400.

[0139] Examples of polymers include poly vinylidene fluoride (PVDF), poly vinylidene difluoride, carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), sodium alginate, lignin, polyurethane (PU), acrylic, and / or polyimide (PI). Examples of the monomer capable of polymerizing to form a polymer include vinyl-based monomers such as vinyl acetate, vinyl chloride, styrene, and vinylidene fluoride; acrylic monomers such as acrylic acid, ethyl acrylate, and butyl acrylate; methacrylic monomers such as methyl methacrylate and methacrylic acid; diene monomers such as butadiene and isoprene; and condensation monomers such as terephthalic acid, ethylene glycol, and caprolactam.

[0140] Without wishing to be bound by theory, it is believed that the inclusion of graphite and / or glassy carbon can enhance the chemical stability and / or electrical conductivity of the porous solid 1400.

[0141] In some embodiments, when the second compound includes Zn-MOF, the Zn-MOF is included in the porous solid 1400. In some embodiments, when the second compound includes Zn-MOF, the Zn-MOF decomposes during the heating to form ZnO, and the ZnO is included in the porous solid 1400.

[0142] In some embodiments, the second compound and the porous solid 1400 includes a polymer stable at a temperature of at least 200 (e.g., at least 250, at least 300, at least 350, at least 400, at least 450, at least 500, at least 550) °C and / or at most 600 (e.g., at most 550, at most 500, at most 450, at most 400, at most 350, at most 300, at most 250) °C.

[0143] In some embodiments, the second compound and the porous solid 1400 includes a polyimide. In general, polyimides can be classified based on the nature of their monomers. Aromatic polyimides are derived from both an aromatic dianhydride and an aromatic diamine. Semi-aromatic polyimides contain one aromatic monomer, meaning either the dianhydride or diamine is aromatic while the other part is aliphatic. Aliphatic polyimides include polymers formed by combining an aliphatic dianhydride and diamine.

[0144] In some embodiments, when the second compound includes a polymer, the mixture 1300 further includes a crosslinking agent. Examples of crosslinking agents include reactive groups or additives such as phenyl ethynyl, maleimide, nadimide (norbomene derivatives), allyl, propargyl, azide, and / or benzocyclobutene. Without wishing to be bound by theory, it is believed that these groups undergo thermal activation at elevated temperatures (e.g., 200- 400 °C), leading to covalent bond formation between polymer chains.

[0145] In some embodiments, the second compound and / or the porous solid 1400 includes silicon, a silicon oxide (e.g., SiO, SiCh), an iron oxide (e.g., Fe2O3, FeO, FesCU), phosphorous, silicon and phosphorus containing compound (e.g., SiP, SiP2, SisP, P doped Si), alumina, zirconia, calcium apatite, copper silicides (e.g., CusSi, CusSi and Cui5Si4), a medium entropy oxide (MEO), and / or r a high entropy oxide (HEO). In some embodiments, the second compound and / or the porous solid 1400 includes LiFePO4, LiMnFePO4, LiCoO2, LiMn2O4, LiNiMnCoO2, LiNiCoAlO2, NaFePO4, and / or NaMnO2. In some embodiments, the second compound and / or the porous solid 1400 includes semi-amorphous carbon, graphitic semi -spherical carbon particles, graphitic graphene nanosheets, and / or graphite powder.

[0146] In some embodiments, the second compound and / or the porous solid 1400 includes silicon. In some embodiments, the silicon is in the form of nanoparticles. In some embodiments, the silicon has a dimension of at least 1 (e.g., at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45, at least 50, at least 55, at least 60, at least 65, at least 70, at least 85, at least 90, at least 95, at least 100, at least 150, at least 200, at least 250, at least 300, at least 350, at least 400, at least 450) nm and / or at most 500 (e.g., at most 450, and most 400, at most 350, at most 300, at most 250, most 200, at most 150, at most 100, at most 95, at most 90, at most 85, at most 80, at most 75, at most 70, at most 65, at most 60, at most 55, at most 50, at most 45, and most 40, at most 35, at most 30, at most 25, at most 20, at most 15, at most 10, at most 9, at most 8, at most 7, at most 6, at most 5, at most 4, at most 3, at most 2) nm.

[0147] In some embodiments, the second compound and / or the porous solid 1400 includes silicon and a polymer. In some embodiments, the second compound and / or the porous solid 1400 includes silicon and a polyimide. In general, in embodiments where the second compound includes a metal, a metal oxide, a semimetal, and / or a ceramic, heating the mixture 1300 sinters the second compound. In general, in embodiments where the second compound includes a polymer, heating the mixture 1300 crosslinks the polymer.

[0148] In general, the pores 1450 are configured so that a liquid or gas may pass therethrough. In some embodiments, the pores 1450 have an average pore diameter of at least 1 (e.g., at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45) nm and / or at most 50 (e.g., at most 45, at most 40, at most 35, at most 30, at most 25, and most 20, at most 15, at most 10, at most 9, at most 8, at most 7, at most 6, at most 5, at most 4, at most 3, at most 2) nm, for example, as determined by nitrogen adsorption-desorption. In some embodiments, the porous solid 1400 has a pore volume of at least 0.05 (e.g., at least at least 0.06, at least 0.07, at least 0.08, at least 0.09, at least 0.1, at least 0.2, at least 0.3, at least 0.4) cm3 / g and / or at most 0.5 (e.g., at most 0.4, at most 0.3, at most 0.2, at most 0.1, at most 0.09, at most 0.08, at most 0.07, at most 0.06) cm3 / g, for example, as determined by nitrogen adsorption-desorption.

[0149] In some embodiments, the porous solid 1400 is microporous. As used herein, a composition or solid being microporous refers to having pores with diameters of from 0.1 (e.g., 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9) nm to 2 (e.g., 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3) nm, for example, as determined by nitrogen adsorption-desorption. In some embodiments, the porous solid 1400 is mesoporous. As used herein, a composition or solid being mesoporous refers to having pores with diameters of from 2 (e.g., 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45) nm to 50 (e.g., 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3) nm, for example, as determined by nitrogen adsorption-desorption.

[0150] In general, the mixture 1300 is heated to a temperature above the sublimation temperature of the first compound and sufficient to cause the sintering and / or crosslinking of the second compound. In some embodiments, the mixture 1300 is heated to a temperature of at least 70 (e.g., at least 80, at least 90, at least 100, at least 150, at least 200, at least 250, at least 300, at least 350, at least 400, at least 450) °C and / or at most 500 (e.g., at most 450, at most 400, at most 350, at most 300, at most 250, at most 200, at most 150, at most 100, at most 90, at most 80) °C. In some embodiments, the mixture 1300 is heated at a heating rate of at least 0.1 (e.g., at least 0.2, at least 0.3, at least 0.4, at least 0.5, at least 0.6, at least 0.7, at least 0.8, at least 0.9 at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45, at least 50, at least 55, at least 60, at least 65, at least 70, at least 75, at least 80, at least 85, at least 90, at least 95) °C / min and / or at most 100 (e.g., at most 95, at most 90, at most 85, at most 80, at most 75, at most 70, at most 65, at most 60, at most 55, at most 50, at most 45, at most 40, at most 35, at most 30, at most 25, at most 20, at most 15, at most 10, at most 9, at most 8, at most 7, at most 6, at most 5, and most 4, at most 3, and most 2, at most 1, at most 0.9, at most 0.8, at most 0.7, and most 0.6, and most 0.5, at most 0.4, at most 0.3, at most 0.2) °C / min.

[0151] In general, the heating of the mixture 1300 can be performed for any appropriate duration. In some embodiments, the heating is performed for a sufficient duration to sublimate all of the first compound in the mixture 1300. In some embodiments, the heating of the mixture 1300 is performed for at least 1 second (e.g., at least 10 seconds, at least 30 seconds, at least 1 minute, at least 5 minutes, at least 10 minutes, at least 30 minutes, at least 1 hour, at least 2 hours, at least 5 hours, at least 10 hours, at least 20 hours, at least 1 day, at least 1 week) and / or at most 1 month (e.g., at most 1 week, at most 1 day, at most 20 hours, at most 10 hours, at most 5 hours, at most 2 hours, at most 1 hour, at most 30 minutes, at most 10 minutes, at most 5 minutes, at most 1 minute, at most 30 seconds, at most 10 seconds).

[0152] In general, the mixture 1300 can include any appropriate amount of the particles 1100 and / or first compound and the powder 1200 and / or second compound. In some embodiments, the mixture 1300 includes at least 0.01 (e.g., at least 0.02, at least 0.03, at least 0.04, at least 0.05, at least 0.06, at least 0.07, at least 0.08, at least 0.09, at least 0.1, at least 0.2, at least 0.3, at least 0.4, at least 0.5, at least 0.6, at least 0.7, at least 0.8, at least 0.9, at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least

[0153] 15, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45, at least 50, at least

[0154] 55, at least 60, at least 65, at least 70, at least 75, at least 80, at least 85, at least 90, at least

[0155] 95, at least 96, at least 97, at least 98, at least 98, at least 99, at least 99.5) wt. % and / or at most 99.9 (e.g., at most 99.5, at most 99, at most 98, at most 97, at most 96, at most 95, at most 90, at most 85, at most 80, at most 75, at most 70, at most 65, at most 60, at most 55, at most 50, at most 45, at most 40, at most 35, at most 30, at most 25, at most 20, at most 15, at most 10, at most 9, at most 8, at most 7, at most 6, at most 5, at most 4, at most 3, at most 2, at most 1, at most 0.9, at most 0.8, at most 0.7, at most 0.6, at most 0.5, at most 0.4, at most 0.3, at most 0.2, at most 0.1, at most 0.09, at most 0.08, at most 0.07, at most 0.06, at most 0.05, at most 0.04, at most 0.03, at most 0.02) wt. % of the particles 1100 and / or the first compound. In some embodiments, the mixture 1300 includes at least 0.01 (e.g., at least 0.02, at least 0.03, at least 0.04, at least 0.05, at least 0.06, at least 0.07, at least 0.08, at least 0.09, at least 0.1, at least 0.2, at least 0.3, at least 0.4, at least 0.5, at least 0.6, at least 0.7, at least 0.8, at least 0.9, at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45, at least 50, at least 55, at least 60, at least 65, at least 70, at least 75, at least 80, at least 85, at least 90, at least 95, at least 96, at least 97, at least 98, at least 98, at least 99, at least 99.5) wt. % and / or at most 99.9 (e.g., at most 99.5, at most 99, at most 98, at most 97, at most 96, at most 95, at most 90, at most 85, at most 80, at most 75, at most 70, at most 65, at most 60, at most 55, at most 50, at most 45, at most 40, at most 35, at most 30, at most 25, at most 20, at most 15, at most 10, at most 9, at most 8, at most 7, at most 6, at most 5, at most 4, at most 3, at most 2, at most 1, at most 0.9, at most 0.8, at most 0.7, at most 0.6, at most 0.5, at most 0.4, at most 0.3, at most 0.2, at most 0.1, at most 0.09, at most 0.08, at most 0.07, at most 0.06, at most 0.05, at most 0.04, at most 0.03, at most 0.02) wt. % of the powder 1200 and / or the second compound.

[0156] In some embodiments, the mixture 1300 includes at least 5 (e.g., at least 6, at least 7, at least 8, at least 9, at least 10, at least 15) wt. % and / or at most 20 (e.g., at most 15, at most 10, at most 9, at most 8, at most 7, at most 6) wt. % of the particles 1100 and / or the first compound.

[0157] As noted above, the sublimated first compound can be condensed to form a solid 1150 of the first compound. In some embodiments, the solid 1150 obtained by condensation has the same chemical composition as the particles 1100. In some embodiments, the solid 1150 obtained by condensation has a different morphology and / or particle size from the original particles 1100. Without wishing to be bound by theory, it is believed that it can be advantageous to use particles 1100 of the first compound for generating porosity, compared, for example, to polymers because the former can be removed by sublimation whereas, in general, a polymeric material would be removed by pyrolysis, which could create harmful gas emissions and / or ash, which could create carbon impurities in the porous solid 1400. Without wishing to be bound by theory, it is believed that it can be advantageous to use particles 1100 of the first compound, compared to metals (e.g., Al, Si-Al alloy), because, in general, during porosity generation, the particles 1100 of the first compound can be removed without the use of acid whereas, in general, the metals would be removed by leaching with a strong acid.

[0158] In general, the mixture 1300 can contain additional materials with a sublimation temperature above the heating temperature used to form the porous solid 1400. Such additional materials can be incorporated into the porous solid 1400. In some embodiments, the mixture 1300 further includes a metal-containing species and the metal-containing species and / or a derivative of the metal -containing species is incorporated into the porous solid 1400 via the heating process. In some embodiments, the metal -containing species includes tin and / or zinc. For example, in some embodiments, the metal -containing species includes a tin- containing species (e.g., tin chloride (SnCh), tin oxide (SnCh)) and the porous solid 1400 includes particles including tin oxide (e.g., nanocrystalline tin oxide). Additionally or alternatively, in some embodiments, the metal -containing species includes a zinc-containing species and the porous solid includes particles including zinc oxide (e.g., nanocrystalline zinc oxide). In some embodiments, heating the mixture 1300 forms a nanocrystalline metal oxide of the metal-containing species in the porous solid 1400. In some embodiments, the nanocrystalline metal oxide has a particle size of at least 1 (e.g., at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45) nm and / or at most 50 (e.g., at most 45, at most 40, at most 35, at most 30, at most 25, at most 20, at most 15, at most 10, at most 9, at most 8, at most 7, at most 6, at most 5, at most 4, at most 3, at most 2) nm. In some embodiments, the mixture 1300 includes at least 0.1 (e.g., at least 0.2, at least 0.3, at least 0.4, at least 0.5, at least 0.6, at least 0.7, at least 0.8, at least 0.9, at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45, at least 50, at least 55, at least 60, at least 65, at least 70, at least 75, at least 80, at least 85) wt. % and / or at most 90 (e.g., at most 85, at most 80, at most 75, at most 70, at most 65, at most 60, at most 55, at most 50, at most 45, at most 40, at most 35, at most 30, at most 25, at most 20, at most 15, at most 10, at most 9, at most 8, at most 7, at most 6, at most 5, at most 4, at most 3, at most 2, at most 1, at most 0.9, at most 0.8, at most 0.7, at most 0.6, at most 0.5, at most 0.4, at most 0.3, at most 0.2) wt. % of the metal-containing species. Without wishing to be bound by theory, it is believed that the presence of the metal -containing species and / or a derivative of the metal-containing species in the porous solid 1400 can improve the electrical conductivity and / or charge storage performance of the porous solid 1400 relative to compositions that do not include a metal- containing species and / or a derivative of the metal -containing species. In general, the metal content of the porous solid 1400 can be evaluated by any appropriate technique, such as inductively coupled plasma (ICP) or by spectroscopic techniques such as energy-dispersive X-ray spectroscopy (EDS)

[0159] In general, the heating discussed above with respect to Figure 1 can be performed under any appropriate atmosphere. In some embodiments, the heating is performed in an atmosphere of air, oxygen, hydrogen, argon, helium, and / or nitrogen. In some embodiments, the heating is performed under vacuum. In some embodiments, the heating is performed in an atmosphere without oxygen. In some embodiments, the heating is performed in an atmosphere with at least 0.1 (e.g., at least 0.2, at least 0.5, at least 1 at least 2, at least 5, at least 10, at least 15, at least 20) vol. % and / or at most 22 (e.g., at most 20, at most 15, at most 10, at most 5, at most 2, at most 1, at most 0.5, at most 0.2) vol. % oxygen.

[0160] In general, the heating can be performed at any appropriate pressure. In some embodiments, the heating is performed at a pressure of at least 1 (e.g., at least 2, at least 5, at least 10, at least 20, at least 50, at least 100, at least 200, at least 500, at least 1000, at least 1500, at least 2000) mbar and / or at most 2026.5 (e.g., at most 2000, at most 1500, at most 1000, at most 500, at most 200, at most 100, at most 50, at most 20, at most 10, at most 5, at most 2) mbar. Without wishing to be bound by theory, it is believed that the sublimation temperature of the first compound can be reduced by reducing the pressure. For example, in some embodiments, the sublimation temperature can be reduced by 50-150 °C depending on the identity first compound and the pressure.

[0161] In some embodiments, the heating is performed at atmospheric pressure to a temperature of 300-400 °C.

[0162] In some embodiments, the method 1000 further includes, prior to the heating the mixture 1300, consolidating the mixture 1300 by mechanically pressing the mixture 1300 into a compacted shape. In some embodiments, mixing the particles 1100 and the powder 1200 to form the mixture 1300 includes pressing the particles 1100 and the powder 1200 using cold pressing or hot pressing. Other methods may also be used to form the mixture 1300 from the particles 1100 and the powder 1200.

[0163] Although the method 1000 has been discussed as including heating, in some embodiments, the method 1000 can be performed without heating and instead a pressure around the mixture 1300 is sufficiently reduced to sublimate at least a portion of the first compound. In some embodiments in which sublimation occurs without heating, the pressure used during sublimation is below 100 mbar. In some embodiments in which sublimation occurs without heating, the mixture 1300 is under vacuum during sublimation.

[0164] Without wishing to be bound by theory, it is believed that vacuum conditions can play an important role in polymer crosslinking. For example, the application of vacuum to sublimate the first compound can create an oxygen-reduced environment that is favorable for free-radical reactions. It is further believed that such conditions are particularly useful for polymers such as collagen nanofibers, poly(lactic acid) (PLA), and metallocene-catalyzed a- olefin / propylene copolymers, which are sensitive to thermal degradation and benefit from low-temperature processing. It is also believed that under vacuum, these materials can undergo enhanced crosslinking when exposed to radiation sources such as gamma rays, which induce free-radical formation in the absence of oxygen, which is a known inhibitor of radical-based mechanisms.

[0165] Electrodes and energy storage applications

[0166] Figure 2a shows a schematic for a method 2000 of forming an anode. While Figure 2 depicts formation of an anode, a similar process can be used to form a cathode.

[0167] In step 2100, polyimide (PI), silicon nanoparticles (SiNPs), and nanostructured terephthalic acid (nano-TPA), which includes a tin-containing species (e.g., SnCh, SnCh) are dispersed in N-methyl-2-pyrrolidone (NMP) to produce a slurry. In the step 2100, nano-TPA corresponds to the particles 1100 of the first compound from the method 1000 (Figure 1) and the PI and SiNPs correspond to the powder 1200 of the second compound from the method 1000 (Figure 1). In addition to or in alternative to NMP, the solvent can include water. In addition to or in alternative to a tin-containing species, a zinc-containing species (e.g., ZnCh, ZnO) can be present.

[0168] In the step 2200, the slurry is coated on a Cu substrate and dried to remove the NMP. Other appropriate substrates may be used. In some embodiments, an aluminium substrate (e.g., aluminium foil) or a carbon substrate can also be used as a substrate.

[0169] In step 2300 the coated substrate is heated, for example in a tube furnace, which causes sublimation of the nano-TPA, sintering of the SiNPs, and crosslinking of the PI. If the tin-containing species includes SnCh, the SnCh is converted into SnO2 nanocrystals. The sublimated TPA can be removed from the heater.

[0170] In step 2400, an anode is obtained. The anode material includes Si, crosslinked PI as a binder, and SnCh nanocrystals. While Figure 2a depicts a method involving certain compounds, the method can also be applied using the various compounds (e.g., first compound, second compound, optional third compound, optional additional material(s)) discussed above.

[0171] In general, the anode can be used in an energy storage device, such as a battery. Figure 2b shows a single cell of a battery 3000 including an anode 2500, a cathode 3100, an electrolyte 3200, and a separator 3300 between the anode 2500 and cathode 3100. The depicted cell of the battery 3000 also includes a wire 3500 and a load 3600 connecting the anode 2500 and the cathode 3100. The battery 3000 includes a plurality of such cells. Examples of batteries include lithium-ion batteries, sodium-ion batteries, calcium -ion batteries, potassium-ion batteries, magnesium-ion batteries, and aluminium-ion batteries. Without wishing to be bound by theory, it is believed that a porous solid of the disclosure can be used as an anode instead of a graphite anode, which can often face limitations due to its relatively low theoretical capacity (e.g., 372 mAh / g) and potential supply shortages.

[0172] Without wishing to be bound by theory, it is believed that Si (e.g., in the form of SiNPs) is a promising lithium-active conversion material due to its relatively high theoretical capacity of 4200 mAh / g, believed to be brought about by the formation of Li22Sis during the lithiation / de-lithiation processes. It is also believed that the relatively low charge potential of Si (<0.4V vs Li / Li+) and its abundance in the Earth’s crust make Si (e.g., in the form of SiNPs) attractive as an electrode (e.g., anode) material for LIBs. However, it is further believed that silicon-containing electrodes (e.g., anodes) may exhibit poor electrochemical performance due to relatively large volume changes (300%) involved in the lithiation / delithiation of silicon, which can result in the pulverization and / or cracking of the electrodes leading to battery failure, and the relatively low electrical conductivity of silicon. However, without wishing to be bound by theory, it is believed that introducing porosity within a Si-containing electrode (e.g., a SiNP-containing electrode) can help mitigate the effects of the significant volume changes associated with the cycling of Si anodes. It is believed that the porous structure can buffer the internal stress applied to the electrode during cycling, thereby reducing (e.g., preventing) pulverization and / or cracking of the electrode structure. Moreover, it is believed that the porous structure can facilitate the penetration of the electrolyte, enhancing the Li+diffusion coefficient within the electrode, shortening the diffusion path for Li+ions, and improving the electrokinetics and cycling life of Si-containing electrodes (e.g., anodes) relative to Si electrodes without porosity. In some embodiments, an electrode of the disclosure has a lithium-ion diffusion value during the second-cycle lithiation process in the range IO'10 5- 10'13 5cm2 / s. In some embodiments, an electrode of the disclosure has a lithium-ion diffusion value during the second-cycle delithiation process in the range IO'10 5- IO'120cm2 / s. In some embodiments, the minimum value of Li-ion diffusion of an electrode of the disclosure during the second- cycle delithiation process is 5 times higher than the minimum value of Li-ion diffusion of an equivalent electrode made without adding particles 1100 of the first compound. In some embodiments, the value of Li-ion diffusion of an electrode of the disclosure during the second-cycle delithiation process at the state of charge equal to 50% is 30-40 times higher than the value of Li-ion diffusion of the electrode made without adding particles 1100 of the first compound.

[0173] In some embodiments, an electrode of the disclosure has a lithium-ion storage capacity of at least 1000 (e.g., at least 1500, at least 2000, at least 2500) mAh / g and / or at most 3000 (e.g., at most 2500, at most 2000, at most 1500) mAh / g.

[0174] In some embodiments, a cell including the anode 2500 and a second electrode including LiFePCU (LFP) has a gravimetric energy density of at least 350 (e.g., at least 400, at least 450, at least 500, at least 550) Wh / kg and / or at most 600 (e.g., at most 550, at most 500, at most 450, at most 400) Wh / kg.

[0175] EXAMPLES

[0176] Chemicals employed included polyimide powder (PI, Mw=50000-80000, Macklin), Si nanoparticles (SiNPs, particle sizes=20-60 nm, >99.9%, Aladdin), conductive carbon (Super P, >99.9%, Thermo Scientific), and carboxymethyl cellulose (CMC, 2%, Canrd Chem). Micrometer-sized terephthalic acid (micro-TPA) was purchased from Sigma-Aldrich (>98%). Nanostructured terephthalic acid containing SnCh was provided by Cambridge Advanced Holding Ltd. Preparation of the nanostructured terephthalic acid containing SnCh is described in WO2023222880 using PET and SnCL at a maximum temperature of 303 °C Example 1 - Fabrication of electrodes

[0177] Silicon nano particles (0.5 g) were mixed with various amounts of nano-TPA powder at a SiNPmano-TPA mass ratio of 5:2, and alternative mass ratios of 6: 1, 5:2, 4:2, and 6:0. Then, the mixtures obtained were transferred into polymeric jars, and ball-milled using a micro vibrating mill device (MSK-SFM-12 M, Hefei Kejing) at 4000 rpm for 20 min under an alumina balkpowder ratio of 10: 1. The mixtures of SiNPs and nano-TPA were used to fabricate electrodes to evaluate the Li-ion storage. For this, 20 mg PI powder was added to 607.5 mg NMP (600 pL) to form a uniform solution. Then, conductive carbon (Super P) and the SiNPs and nano-TPA mixture were added into the PI solution to form ratios of Si: TPA: PI: conductive carbon = of 6:1 : 1 :2, 5:2:2:1, 4:2:2:2, and 6:0:2:2. Each mixture was subjected to ultrasonic vibration for 20 min to obtain uniform dispersion then stirred for 10 h, and the resulting uniform slurry was coated on Cu foil, and dried at room temperature for 10 min, and then at 100 °C for 2 h under vacuum to remove the NMP.

[0178] Example 2 - Fabrication of porous Si anode enhanced by decorated cross-linked PI binder and SnCh

[0179] The electrodes described in the previous example were thermally treated at temperatures of 250 or 350 °C with the heating rate of 5 °C / min under an Ar-4% EE stream in a tube furnace, with a dwell time at the maximum temperature of 2 h. The thermal process at 350 °C led to the formation of porous Si anode with cross-linked PI binder and SnCh. As the nano-TPA was doped with SnCh, the thermal treatment produced a cross-linked PI binder decorated with SnCF nanocrystals. After completion of the thermal treatment, the temperature was reduced to room temperature under the same gas flow. The electrodes obtained were pressed under 10 MPa pressure for 30 s, and then cut into discs (diameter ~12 mm). The obtained electrodes were used to assemble coin cells, for half-cell and full-cell characterizations. For comparation, electrodes were fabricated with carboxymethyl cellulose (CMC)as the binder using the same procedure as mentioned above except for the thermal treatment.

[0180] Th 2025-type coin cells were assembled in an argon-filled glovebox. Cell consisted of a polypropylene separator and 1.0 M lithium hexafluorophosphate (LiPFe) in ethylene carbonate (EC) and ethyl methyl carbonate (EMC) mixture (ECZEMC = 3:7 Vol%) with an extra 10.0% fluoroethylene carbonate (FEC), as the electrolyte. A metallic Li disc was used as the counter / reference electrode in half-cells, while LiFePCU (LFP) electrodes were used as the cathode in the full cell configuration. The cathode was prepared by preparing a slurry of LFP particles (Dynanonic), Super P, and PVDF at a mass ratio of 8: 1 : 1. The homogeneous slurry was coated onto aluminium foil and dried under a vacuum at 80 °C for 24 h.

[0181] Example 3 - Characterization

[0182] X-ray diffraction (XRD) characterization was conducted using a D8 ADVANCE system using Cu-Karadiation (1.5405 A) in the range 29=10-80°, with a step size of 0.03° and time per step of 3 s. Fourier transform infrared (FTIR) examination was performed using a VERTEX70 system employing a KBr pellet as the reference electrode, in wavenumber ranging 4000-400 cm'1with a resolution of 0.4 cm'1. X-ray photo-electron spectroscopy (XPS) was carried out using a Thermo Scientific K-Alpha instrument, and employing a non- monochromatized Al Ka source (1486.6eV) in an UHV chamber. The axis of the analyzer and photon beam direction were adjusted at 70°, and photoelectrons were collected toward the direction perpendicular to the surface. The calibration was made using the aliphatic component of the C Is peak at 284.8 eV. The area of the samples prepared for analysis was 400 x 400 pm2. The pass energy for the full and fine spectra was adjusted at 150 and 50 eV with the resolution of 1 and 0.1 eV, respectively. Advantage software was used for the background subtraction (Shirley type background) and curve fitting analysis. Line syntheses of elemental spectra were performed using Gaussian-Lorentzian (70:30) curve fitting. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were conducted using a JEM-2100-plus and ZEISS EVO 18, respectively. The electrodes were immersed in dimethyl carbonate (DMC) overnight before SEM. An SDT Q600 thermal analyzer equipped with alumina crucibles was used for differential scanning calorimetry (DSC), and thermal gravimetry analysis (TGA). Thermograms were obtained at the heating rate of 20 °C min'1under an Ar flow rate of 100 mL min'1. The specific surface area was calculated from the BET plots obtained by N2 adsorption / desorption isotherms conducted on a ASAP 2020 Plus Physisorption equipment.

[0183] Galvanostatic charge-discharge measurements were performed at 0.01-1.5 V (halfcells) and 2.5 and 3.6 V (full -cells) at 25 °C using a LAND battery test system (CT2001A, Wuhan Land Electronic Co. Ltd., China). CHI 660E electrochemical workstation was used to conduct cyclic voltammetry (CV) measurements at the scan rate and voltage range of 0.1 mV s'1and 0.01-3.0 V vs Li / Li+, respectively, and the electrochemical impedance spectroscopy (EIS) at an AC oscillation amplitude of 5 mV within the frequency range of 100 kHz to 10 mHz.

[0184] Table 1. Abbreviation of various samples characterized.

[0185] Figure 3a (top) shows the XRD pattern of the micro-TPA, with peaks matching with terephthalic acid (CsHeCU) with anorthic crystalline structure (ICDD: 00-031-1916) as exhibited in Figure 3a (bottom). According to the TG thermogram of Figure 3b, the micro- TPA experienced almost 100% mass loss in the temperature window of 290-416°C during heating at 20 °C / min under Ar, which corresponds to the sublimation of the material. The SEM morphology of micro-TPA is characterized by the presence of particles with various sizes in the range 10-100 pm as can be seen in Figure 3c.

[0186] The XRD pattern of nano-TPA (Figure 3a (middle)) is similar to that of micro-TPA, with all peaks assigned to that of anorthic structured CsHeCU (ICDD: 00-031-1916).

[0187] According to the TG thermogram of Figure 3b, nano-TPA experienced a three-stage mass loss: The first stage at 60-150 °C (6.6 % mass loss) was attributed to the evaporation of moisture; the second stage at 254-358 °C was due to the sublimation of the material, and the third stage at 416-770 °C was related to the decomposition of the remaining organic matter. The remaining material was characterized to be SnCh (11.9 mass%), which is stable through heating at greater temperatures. SEM micrograph of nano-TPA (Figure 3d) was different from micro-TPA, showing a nanostructured morphology containing particles of typically less than 100 nm, agglomerated into larger particles.

[0188] High-resolution TEM micrographs recorded on nanoparticles (Figure 3e) reveal the presence of SnCh nanocrystals with sizes of typically less than 6 nm decorated on TPA, as confirmed by the fast Fourier Transform pattern of Figure 3f. The spot observed in the pattern is related to the (110) crystalline planes of tetragonal SnCh with the interlayer spacing of 0.33 nm, which is decorated on nanostructured TPA during the preparation of the sample. TEM characterization of the CsHsCU phase in the sample was not possible due to the instability of the organic material under the high voltage electron beam applied. Without wishing to be bound by theory, it is believed that the SnCh phase could not be identified in the XRD pattern of Figure 3a (middle) was due to the relatively small crystalline domain sizes of the crystals.

[0189] Figure 3j shows a bright field TEM micrograph of nano-TPA and Figure 3k shows an electron diffraction pattern recorded on the image, exhibiting rings and spots corresponding to the crystalline planes of SnCh. Figure 31 shows a high magnification TEM micrograph recorded on a SnCh nanocrystal and Figure 3m shows a FFT pattern recorded on the nanocrystal. Figure 3n shows the EDS mapping analysis showing the elemental distribution of C, O, and Sn. The existence of SnCh was further proved, based on the EDS mapping analysis shown in Figure 3n. Hydrogen cannot be detected by EDS.

[0190] The nano-structured tin doped TPA powder (nano-TPA) was further characterized by X-ray photoelectron spectroscopy (XPS), and the results obtained are shown in Figures 3g-3i . The C is core-level spectrum (Figure 3g) is dominated by a peak at 284.8 eV, representing the presence of graphitic sp2carbon with C-C bonding. An additional 7t-7t* bond representing the benzene ring can also be detected at 291.3 eV, confirming the presence of TPA. According to the fitted O ls core level XPS spectrum (Figure 3h), three peaks can be identified located at 531.5, 532.0, and 533.3 eV. These peaks can be assigned to O-Sn, O-C, and C-O=C, respectively, which confirmed the presence of TPA and tin oxide. Also, the Sn 3d spectrum of the sample (Figure 31) revealed the presence of peaks at 487.1 and 495.5 eV which indicated the existence of Sn4+5 / 2 and Sn4+3 / 2, respectively, thus the presence of tin oxide in nano-TPA, which was in agreement with the TEM observations of Figures 3e and 3f. Without wishing to be bound by theory, it is believed that nano-TPA and micro-TPA can be used in a electrode to develop a porous cross-liked structure which can improve the electrochemical performance of the cell, for example in an electrode employing Si nanoparticles (SiNPs) as the active material and PI as the binder.

[0191] From top to bottom, the XRD patterns for nano-TPA, SiNPs, and PI are displayed in Figure 3o. Powder Diffraction File (PDF) numbers for Si and TPA are included for comparison. In the XRD pattern of SiNPs, five intense diffraction peaks were be observed at 29 =28.4°, 47.3°, 56.1°, 69.1° and 76.4°, which were attributed to the (1 1 1), (2 2 0), (3 1 1), (4 0 0), and (3 3 1) crystalline planes in the face-centered cubic (FCC) structure of silicon. Three intense peaks were also observed in the TPA patterns, at around 29 =17.3°, 25.1° and 27.6°, attributed to the (1 1 9), (9 1 1) and (-1 9 1) crystalline planes in the Anorthic structure of TPA. The sharp diffraction peaks reveal the highly crystallized nature of the sample. Meanwhile, two broad diffraction peaks appeared at 29 = 19-39° and 29 = 49-59°, which correspond to the amorphous structure of polyimide. Figure 3p shows the XRD pattern of the mixture containing SiNPs and nano-TPA with mass ratio of 5:2 after 29 min ball milling, where sharp peaks corresponding to Si and TPA can be observed, demonstrating that the ball milling process did not change the crystal structures of these two materials, even though they were thoroughly mixed. PDF numbers for Si and TPA are included for comparison.

[0192] Example 4 - Thermal behaviour

[0193] To understand the possible interactions between the polyimide (PI) binder and TPA, mixtures of PI and nano-TPA with a 1 : 1 mass ratio with different processing were subjected to XRD analysis. The mixture was characterization without any further processing, and alternatively, after heating at 259 °C or 359 °C. These samples were labelled as PI@nano- TPA, PI@nano-TPA@25 , and PI@nano-TPA@359, respectively. Similar experiments were conducted using micro-TPA, and the samples were named as PI@micro-TPA, PI@micro- TPA@259, and PI@micro-TPA@359, respectively. The XRD patterns of these samples are shown in Figure 4a.

[0194] Figure 4a (second from bottom) shows the patterns of the powder mixture, which is mixed of SiNPs and nano-TPA powder with 5:2 mass ratio after 29 min ball milling. The sharp peaks of Si and TPA were both observed, demonstrating that ball milling process did not change the crystal structures of these two materials and these two materials have been well mixed.

[0195] For all samples, the broad peak at 29 = 1 -3 ° correspond to the amorphous structure of polyimide. In XRD patterns of PI@nano-TPA (Figure 4a (second from bottom)), PI@nano-TPA@259 (Figure 4a (second from top)), PI@micro-TPA (Figure 4c (second from bottom))), and PI@micro-TPA@250 (Figure 4c (second from top)), the peaks related to TPA can be observed, but when the temperature was increased to 350 °C, the sharp peaks related to TPA disappeared, and instead, five new peaks at 29 = 26.6°, 33.9°, 37.9°, 43.4° and 51.8° emerged in the pattern of PI@nano-TPA@350 (Figure 4a (top)). These peaks were attributed to the (1 0 1), (0 1 1), (0 0 2), (1 0 2), and (1 1 2) crystalline planes in the tetragonal structure of SnCh. The appearance of SnCh XRD peaks in PI@nano-TPA@350 was in agreement with the TEM micrographs of Figures 3e and 3f, confirming the presence of SnCh nanocrystals decorated on the surfaces of nano-TPA. The disappearance of TPA peaks was due to the sublimation of the terephthalic acid during the prolonged heating at 350°C for 2 hours, as suggested by the TGA thermogram of Figure 3b. The sublimated TPA was condensed downstream of the tube of the tube furnace at the colder part of the furnace, producing a white deposit. The XRD pattern of this deposit (Figure 4b) confirms the successful recovery of the TPA material. Its morphology was substantially different from that of the nano-TPA (Figure 3d) characterized by the presence of relatively large particles with dimensions typically around 100 pm.

[0196] The results suggests that nano-TPA mixed with PI can be sublimated to leave nanocrystals of SnCh behind, while the sublimated TPA can be condensed into micrometersized TPA downstream the tube furnace. The same sublimation-condensation behaviour was observed using micro-TPA and polyimide heated at 350°C, with a white deposit corresponding to TPA collected downstream of the tube of the tube furnace in PI@micro- TPA@350 °C. The XRD pattern of this sample (Figure 4c (top)) exhibits the semi-amorphous structure of PI.

[0197] The evaporation of TPA from the electrode containing Si and PI could alter the surface area and the porosity structure of the electrode left behind. To examine this, the mixture of SiNPs and PI with 1 : 1 mass ratio was heated at 350 °C, and the sample obtained (Si@PI@350) was characterized using nitrogen adsorption-desorption experiment. The same experiment was conducted on a Si@PI@nano-TPA@350 sample with mass ratio of 5:2:2: 1, and the results obtained are shown in Figure 5.

[0198] The adsorption / desorption of Si@PI@350 and Si@PI@nano-TPA@350 (Figures 5a and 5c, respectively) demonstrate the Type III isotherms characteristics of macroporous structures. The BET surface area of Si@PI@350 (35.8 m2 / g) was slightly larger than that of Si@PI@nano-TPA@350 which may be due to the re-organization of SiNPs and PI chains during sublimation of TPA, leading to the closing of a portion of pores. However, the pore size distribution of Si@PI@nano-TPA@350 (Figure 5d) showed a more developed pore structure with an average pore diameter and pore volume of 25.1 nm and 0.17 cm3 / g, greater than those of Si@PI@350 (Figure 5b) of 15.5 nm and 0.14 cm3 / g, respectively. Moreover, the porosity distribution of Si@PI@nano-TPA@350 shows a peak at around 18 nm, while the peak is less obvious in Si@PI@350 located at greater value of around 33 nm.

[0199] Without wishing to be bound by theory, it is believed that such porosity alterations achieved by the sublimation of nano-TPA could enhance the electrochemical performance of the resulting electrode. The use of micro-TPA could also alter the surface characteristics of Si-PI structure, as can be seen in Figures 5e and 5f, recording a BET surface area, average pore diameter and pore volume of 37.6 m2 / g, 11.1 nm and 0.10 cm3 / g, respectively, for Si@PI@micro-TPA@350. The surface properties of samples based on N2 adsorption / desorption trials are shown in Table 2, from which the greater values of pore diameter and pore volume in Si@PI@nano-TPA@350 is evident. Such alterations provide the sample with an opportunity to accommodate the volume changes occurring during the Li-ion insertion and extraction processes.

[0200] The influence of thermal treatment on the mixtures of PI and TPA was further confirmed using TGA and DSC of PI@nano-TPA (1 : 1 mass ratio) under Ar. As shown in Figure 5g, a mass loss of only 14.7% was observed upon heating the mixture to 250 °C, which is mostly attributed to the removal of moisture and other organic molecules from the surfaces of the materials. This indicates the relative thermal stability of TPA material. As can be seen from DSC curve of Figure 5g, there is a sharp endothermal peak at 318 °C, corresponding to the sublimation of TPA, which was in agreement with Figure 3e, and also consistent with typical thermal stability expected for TPA. At 350 °C, the total mass observed was recorded at 50.1%. Considering the mass ratio of PI and nano-TPA (1 : 1) and the initial mass loss of the mixture (14.7%), it can be concluded that almost all the TPA the mixture was removed when the temperature was increased to 350 °C, while the SnCh nanocrystals (11.9 mass% of the nano-TPA, based on Figure 3e) were left behind. The total sublimation of TPA at 350 °C was also consistent with the XRD results of Figures 4c and 4g.

[0201] To investigate the thermal stability of the PI@nano-TPA@350 sample, the PI@nano- TPA@350 and PI were tested using the TG-DSC. For example, the TG-DSC thermograms of PI@nano-TPA@350 and PI are shown in Figures 5h and 5i, respectively. According to Figure 5h, PI@nano-TPA@350 experienced a mass loss of only around 9% through heating of the sample to 500 °C. This mass loss was measured to be around 7% for the PI sample (Figure 5i), indicating the excellent thermal stability of both samples. The slightly greater mass loss observed in PI@nano-TPA@350 can be attributed to its relatively greater porosity allowing it to adsorb more moisture. The results obtained show the sublimation of TPA during the thermal treatment of its mixture with PI, and the excellent thermal stability of porous PI obtained after the thermal process, which is a significant advantage for LIB electrode materials. These observations provide insights on the fabrication of porous electrodes through the use of TPA. The porosity obtained using nano-TPA is greater with a peak of distribution around 18 nm, lower than in the sample obtained using micro-TPA (33 nm).

[0202] Table 2. The surface properties of samples based on N2 adsorption / desorption experiments

[0203] Example 5 - Surface chemistry of PI@nano-TPA and PI@nano-TPA@350

[0204] To study the influence of adding nano-TPA into PI and the effect of thermal treatment, for the mixed nano-TPA and polyimide powder with the mass ratio of 1 : 1 (PI@nano-TPA) and after thermal treating at 350°C (PI@nano-TPA@350) the surface chemistry was studied using XPS and FTIR measurements. As shown in Figures 6a and 6d, the C Is core level XPS spectrum of both samples could be separated into four peaks, at 284.8, 286.4, 289.0, and 291.3 eV, for PI@nano-TPA and 284.8, 286.3, 288.5, and 291.2 eV for PI@nano-TPA@350, which represented the C-C, C-O, C=O and 7t-7t* bond of the TPA and PI. The intensity and area of these peaks exhibited notable disparities, allowing the quantification of the effect of the annealing process on the surface composition of the samples by calculating the relative area of the peaks. The results are presented in Table 3. As can be observed, the relative peak areas related C=O and 7t-7t* bonds decreased from 16.40% and 5.41% in PI@nano-TPA to 6.70% and 2.18% in PI@nano-TPA@350, respectively, indicating the sublimation of TPA. Meanwhile, the value of the relative area for C-C peak in PI@nano-TPA (72.48%) does not significantly vary after the thermal treatment (76.07%), but that of C-0 sharply increases from 5.71% to 15.05%, confirming the separation of TPA from PI. The sharp decrease in the XPS peak areas for C=O (from 16.40% to 6.70%) and 7t-7t* transitions (from 5.41% to 2.18%) after thermal treatment are consistent with the removal of nanostructured TPA from the PI+TPA mixture. Since TPA was present in a nanostructured form, it had a relatively high surface-to-volume ratio and likely dominated the surface composition of the material. Given that XPS is a surface-sensitive technique, even a relatively small amount of surface-enriched nanostructured TPA would contribute significantly to the observed C=O and 7t-7t* signals. Once TPA sublimated during heating, the surface became enriched with the remaining polyimide, which has fewer accessible carbonyl groups and more buried aromatic structures, explaining the substantial reduction in both C=O and 7t-7t* signal intensity in the XPS spectra.

[0205] From the N 1 s spectra of samples, shown in Figure 6b, the peaks at 397.4 and 400.5 eV in PI@nano-TPA are assigned to =N+- and -NH- of PI. After the heating process, the =N+- peak shift to a higher value of 398.5 eV (Figure 6e). This shift was due to the formation of hydrogen bonding between Sn-0 and the N-H of polyimide chain. As shown in the N Is spectrum of PI@nano-TPA@350 (Figure 6e), an extra peak appeared at 402.4 eV, which corresponds to formation of charge transfer complex structures (CTCs).

[0206] Without wishing to be bound by theory, it is believed that the formation of CTCs among the molecular chains of polyimide increases the packing density, thereby creating a more compact structure that promotes the electron transfer kinetics, and reduces the electrochemical resistance within the electrode made using the PI binder. From O ls spectra of PI@nano-TPA (Figure 6c), the O-Sn peak was detected at 531.5 eV which indicted the presence of tin in the PI@nano-TPA. The relative XPS area 0=C-0 peak decreased after the heating process (Table 3), which was also evidence for the removal of TPA. According to the O ls spectrum of PI@nano-TPA@350A (Figure 6f) a peak shift, similar to that of =N+- peak discussed above, was observed for the Sn-0 peak, from 531.5 to 531.1 eV. This peak shift can also be due to the CTC formation. The XPS results further confirmed the presence of tin in both samples, and the sublimation of TPA and CTCs formation upon thermal treatment. These results explain the greater electrochemical performance the thermal treated electrode (Si@PI@nano-TPA@E-350), as discussed below.

[0207] Table. 3. The relative XPS peak area extracted from the C Is spectra of Figure 6.

[0208] FTIR spectra of various samples was characterized using FTIR, and the resulting spectra are shown in Figures 6g-6j. The spectra recorded on PI (Figure 6g), PI@nano-TPA (Figure 6i), and PI@nano-TPA@350 all exhibited characteristic peaks at around 1369 and 879 cm'1, corresponding to the C-N of imide rings and C=C of the terephthalic acid, respectively. The C-N peak in PI-nano-TPA (1369 cm'1) experiences a red shift of 8 cm'1after the heat-treatment, suggesting the formation of CTCs among polyimide molecular chains. These observations suggest that the addition of nano-TPA does not affect the formation of CTCs, which is beneficial since the formation of charge transfer complex structures provide a more compact structure, promoting the integrity of electrodes employing PI as the binder.

[0209] The peak corresponding to the C=C bond of TPA which was detected at 879 cm'1in nano-TPA disappeared after heating at 350 °C, as can be seen from Figures 6g and 6j. This observation is explained by the sublimation of TPA during the heat-treating process, providing porosity to the corresponding electrodes such as Si@PI@nano-TPA@E-350. Moreover, the peak corresponding to O-Sn-O were observed at 781 cm'1in all samples, with the exception of PI, confirming the successful transfer of tin from nano-TPA into the crosslinked PI prepared at 350 °C. The results obtained suggest the successful preparation of SnCh-decorated porous PI by the application of nano-TPA and a simple thermal treatment, while the TPA material can be recycled by the condensation of sublimated TPA. Without wishing to be bound by theory, it is believed that the SnCh-decorated porous PI with CTC structure obtained at 350 °C can provide a more robust platform to accommodate the volume changes involved in Li-ion insertion and extraction in / out of Si nanoparticles, thereby improving their electrochemical properties.

[0210] Figures 6k-6o show FTIR spectra of TPA, PI, PI@nano-TPA, PI@nano-TPA@250, and PI@nano-TPA@350, respectively. As shown in Figures 6k-6o, there was a peak around 3100 cm'1in all samples, which corresponds to the O-H group. Without wishing to be bound by theory, it is believed that the stability of this bond during the thermal treatment could promote hydrogen bonding with oxide layers around SiNPs, as shown in the TEM micrographs of Figures 6p and 6q, and that such bonding could promote the integrity of the Si@PI@nano-TPA@E-350 electrodes over prolonged charge-discharge events. Example 6 - Li-ion storage performance of electrodes

[0211] Electrodes were fabricated by inserting SiNPs into PI@nano-TPA, PI@nano- TPA@250, and PI@nano-TPA@350 (as described in Example 2). The electrodes prepared in this manner are referred to as Si@PI@nano-TPA@E, Si@PI@nano-TPA@E-250, and Si@PI@nano-TPA@E-350, respectively. Electrodes were also fabricated using PI binder alone thermally treated at 350 °C and CMC binder alone, both without the addition of nano- TPA. These electrodes were referred to as Si@PI@E-350 and Si@CMC@E, respectively.

[0212] The initial galvanostatic discharge / charge curves of the prepared electrodes at the voltage range of 0.01 to 1.5 V are shown in Figure 7a. As can be seen, Si@PI@nano- TPA@E-350 displayed an initial discharge capacity of 3224.8 mAh g'1at 100 mA g , which is higher than those of Si@PI@nano-TPA@E-250 (2541.6 mAh g'1), Si@PI@E-350 (2547.3 mAh g'1), Si@CMC@E (1944.4 mAh g'1), and Si@PI@nano-TPA (1443.4 mAh g'1). Without wishing to be bound by theory, it is believed that the presence of well -structured porosity within Si@PI@nano-TPA@E-350 can allow for the diffusion of the electrolyte into the electrode, thereby shortening the Li-ion diffusion and promoting the accessibility of the electrolyte to Si active material, and thus improving the Li-ion storage capacity.

[0213] Figure 7b shows the galvanostatic discharge-charge profiles of Si@PI@nano- TPA@E-350 electrode recorded at a current density of 100 mA / g for the first cycle, and 200 mA / g for subsequent cycles. The voltage-capacity profile of the first discharge cycle exhibited a sloped line starting from around 1.05 V, which disappeared in the subsequent discharge cycles. This sloped line was attributed to the formation of a solid electrolyte interphase (SEI) layer. Subsequent discharge / charge curves showed an excellent consistency, suggesting the stability of the SEI layer, and desirable cycling performance of the Si@PI@nano-TPA@E-350 electrode.

[0214] The Li-ion insertion / extraction behaviour of Si@PI@nano-TPA@E-350 was also evaluated by the cyclic voltammetry (CV) at 0.1 mV s'1between 0.01 and 3 V (Figure 7c). The initial discharge and charge curves exhibited one broad reduction peak starting at 1.05 V, assigned to the formation of SEI, a rather sharp reduction peak starting at 0.25 V and two oxidation peaks at 0.3 V and 0.5 V. These peaks are in agreement with the discharge / charge curves of Figure 7a, illustrating the alloying / dealloying reaction mechanism of the Si anode from an electrochemical perspective. Throughout the course of four cycles, the intensity of the peaks gradually amplified, suggesting a progressive activation of the Si anode. The Si@PI@nano-TPA@E-350 electrodes were fabricated using Si: PI: nano-TPA: Super P mass ratios of 5:2:2: 1, 6: 1 : 1 :2, 4:2:2:2 and 6:2:0:2. In all these electrodes, the mass ratio of polyimide : terephthalic acid was considered to be 1 : 1. The electrochemical performances of these electrodes were compared with each other, and to that of Si@CMC@E, with Si: Super P: CMC ratio of 6:2:2. The Li-ion storage cycling performances of these electrodes are shown in Figures 7j and 7k, in terms of specific capacity and coulombic efficiency, respectively. From the results obtained, the Si@PI@nano-TPA@E-350 with the formulation of 5:2:2: 1 appeared to generate the optimum performance. Therefore, this ratio was used for further characterization of the electrodes.

[0215] Figures 7d and 7e and Table 4 show the Li-ion storage cycling performance of various electrodes, including Si@PI@nano-TPA@E-350 and Si@CMC@E. As can be observed, the Si@PI@nano-TPA@E-350 outperformed other electrodes, exhibiting a reversible capacity of 2355.3 mAh / g after 120 Li-ion insertion and extraction cycles, which was considerably greater than the reversible capacity of other electrodes including Si@PI@nano-TPA@E (482.3 mAh / g). These results highlight the influence of the thermal treatment process in creating SnCF-decorated porous cross-linked PI network containing charge transfer complex structures, which improved the cycling stability of the Si nanoparticles.

[0216] Table. 4. Li-ion storage performances of different electrodes after 120 cycles at the current density of 200 mA g’1.

[0217] The porous CTC structure obtained through the heating process not only had an impact on the cycling stability of the electrode, but also on its rating performance, as shown in Figure 7f. This enhancement was more obvious at higher current densities. As can be observed in Figures 7d-7f, the Si@PI@nano-TPA@E electrode, fabricated without the thermal processing step, exhibited the lowest cycling and rate performances among the sample. Under the current density of 200 mA / g, this sample exhibited a capacity of 482.8 mAh / g after 120 cycles (Figure 7d) and a capacity of 377 mAh / g at 2000 mA / g after 25 cycles (Figure 7f). Notably, the performance of this electrode was inferior to that of Si@CMC@E fabricated using CMC binder, which provided a capacity of 870.8 mAh / g after 120 cycles at 200 mA / g, and 573.5 mAh / g after 25 cycles at 2000 mA / g (Figure 7f). Without wishing to be bound by theory, it is believed that the PI binder in Si@PI@nano-TPA@E does not provide a CTC cross-linking structure, resulting in the inadequate performance of the binder system to maintain the integrity of electrode over cycling. In contrast, the electrochemical performances of Si@PI@nano-TPA@E-350 is the greatest within the electrodes, which provided a Li-ion storage capacity of 2408.9 mAh / g after 120 cycles at 200 mA / g (Figure 7d) and 1964.7 mAh / g after 25 cycles at 2000 mA / g (Figure 7f).

[0218] As can be seen from Figure 7f, the Si@PI@nano-TPA@E-250 exhibited a slightly higher rate performance than the Si@PI@E-350, although the CTC structure of PI is well developed at 350°C in comparison with 250 °C. Without wishing to be bound by theory, it is believed that the greater rate performance of Si@PI@nano-TPA@E-250 may be due to the presence of terephthalic acid, providing hydrogen bonding within the electrode that enhances the stability over cycling. It is also believed that the unsaturated benzene rings provided by TPA can also provide conductive channels that enhance the rate capability of the electrode. At 350 °C, the CTC structure was adequately formed within the PI chains, improving the electrochemical performance of electrodes. Moreover, the porous structure formed by the sublimation of nano-TPA, in combination with the introduction of SnCh decorated on the porous CTC structure, collectively improved the cycling performance and rate capability of the Si@PI@nano-TPA@E-350 as can be seen in Figures 7d-7f. The greater performance of this electrode can also be observed from the cycling experiment conducted at a current density of 800 mA / g (Figures 7g and 7h).

[0219] In Figure 7g, at the current density of 800 mA / g the Li-ion storage capacity of Si@PI@nano-TPA@E-350 was recorded to be 1354 mAh / g after 150 cycles, which was substantially greater than that of Si@PI@E-350 (13.6 mAh / g) and Si@PI@micro-TPA@E- 350 which was fabricated using micro-TPA (818.1 mAh / g). Even under an enhanced current density of 5000 mA / g and after 300 cycles, the Si@PI@nano-TPA@E-350 electrode was able to exhibit a reversible capacity 651 mAh / g (Figure 8a). At an ultra-high current density of 10,000 mA / g, the electrode maintained a capacity of 283 mAh / g after 1,000 cycles (Figure 8b), demonstrating its capability to perform under various conditions. The Li-ion storage performance of Si@PI@nano-TPA@E-350 was compared with alternative systems in the literature, as shown in Figure 7i and Table 5. Figure 5g, left panel, shows the electrochemical performances of various electrodes at the current density of 200 mAg'1after 100 cycles. Figure 5g, right panel, shows similar comparisons at higher values of current density. The Si@PI@nano-TPA@E-350 electrode showed a specific capacity of 2645 mAh / g at 200 mA / g after 100 cycles. In contrast, the SiMPs@GO / ssDNA electrode made of self-assembled 3D interconnected graphene oxide and silicon micro-particles using singlestrand DNA could provide a capacity of 1958 mAh / g under the same condition. Similarly, the capacity of other electrodes including micro-SiOxcombined with 3D binder system of rigid anion gum arabic, acrylic random copolymer, and carbon nanotubes (SiOx@ARC9GA2), freestanding N-doped porous carbon nanofibers sheathed pumpkin-like Si / C composites (Si / C- ZIF-8 / CNFs), and flexible conductive Si / CNT composite (Si / CNT) could deliver capacities of 1300, 1045 and 1275 mAh / g, respectively. These observations confirm the clear advantages of Si@PI@nano-TPA@E-350, including its relatively simple fabrication process, the absence of expensive and / or hazardous chemicals, and its relatively good electrochemical performance, all achieved without the use of complex material systems.

[0220] Table 5. The Li-ion storage performance of various electrodes after 100 cycles, extracted from Figure 5g.

[0221] As shown in the right panel of Figure 5g, at the higher current density of 800 mA / g, the Si@PI@nano-TPA@E-350 electrode shows a relatively good capacity of 1567 mAh / g after 100 cycles compared with that of Si / CPPy-NT@1000 made of Si nanoparticles with ID nano-carbonaceous fillers featuring nanotubular morphology and N doping and SiO-PVPA with micro-SiO and graphite using poly(vinylphosphonic acid), delivering a capacity of 1100 mAh / g (400 mA / g) and 574 mAh / g (500 mA / g), respectively. The SiNPs@CNTs modified by hydroxypyrene (Si@(POH-AOCNTs)) and Si -fluorinated binder (Si / F -binder) also showed relatively good electrochemical performances, delivering capacities of 1400 mAh / g (800 mA / g) and 1550 mAh / g (1000 mA / g), respectively, due to the presence of suitable binder systems.

[0222] Example 7 - Electrokinetics

[0223] The electrode treated at 250 °C (Si@PI@nano-TPA@E-250) was found to contain TPA due to the fact that 250 °C is lower than the sublimation temperature of nano-TPA (318 °C), as shown in Figure 5g, and no deposit was observed downstream of the tube furnace. The performance of the this electrode was found to be inferior to Si@PI@nano-TPA@E-350 but superior to the electrode without TPA thermally treated at 350°C.

[0224] The effect of heating temperature on the electrochemical impedance of Si@PI@nano- TPA@E electrodes thermally treated at various temperatures (200, 250, 300 and 350 °C) was investigated by electrochemical impedance spectroscopy (EIS) at an AC amplitude of 5 mV within the frequency range 0.01-1000000 Hz. The Nyquist plots of these electrodes as well as the of Si@PI@E-350 is shown in Figure 9a, with simulated circuit used to calculate the impedance of electrodes shown in Figure 9g.

[0225] In the EIS curves, the semicircles at the high frequency region of the spectra corresponds to the charge transfer resistance (Ret), where a smaller semicircle diameter corresponds to a smaller electron transfer resistance. The oblique line at the low frequency region corresponds to the Li-ion diffusion impedance (Rs). The values of resistance obtained based on the Nyquist plots for various electrodes are shown in Table 6. As can be observed, the Ret of the Si@PI@nano-TPA@E electrodes become gradually smaller as the temperature of heat-treatment increased, providing a minimum value at 350 °C (98.89 Q). Without wishing to be bound by theory, it is believed that this trend was due to the gradual development of the CTC structure between the PI molecular chains by increasing the temperature, providing a more compact electrode modified by cross-linked PI. Compared to the Si@PI @E-350 electrode (214.7 Q), Si@PI@nano-TPA@E-200 exhibited a higher Rct value (253.8 ) compared to the Si@PI@E-350 electrode (214.7 Q), which may be attributed the incomplete development of the CTC structure at lower temperatures, resulting in poorer electrokinetic performance. By increasing the temperature from 300 to 350 °C, the value of Rct decreased by 46% from 184.9 to 98.9 . This sharp reduction of the Rct can also be influenced by the sublimation of TPA, leaving a porous cross-inked structure doped with SnCF nanocrystals. Such nanocrystals further provide for the fast multidirectional charge transfer. Without wishing to be bound by theory, it is believed that the inclusion of SnCE within the porous structure enhances the electrical conductivity, as can be evidenced by the reduced charge-transfer resistance (Rct), thereby improving the electrode's rate capability.

[0226] Table 6. Impedance data extracted from Figure 9a.

[0227] The diffusion coefficient of Li+into / out of the electrodes (Du+) was further evaluated by galvanostatic intermittent titration technique (GITT). Figure 9b shows the roomtemperature GITT curves of Si@PI@nano-TPA@E-350 and Si@PI@E-350 electrodes recorded during the second cycle at the current density of 200 mA / g, where the pulse, and relaxation times were adjusted to 60 min and 30 min, respectively. The data obtained was employed to calculate the values of Du+ at various voltages using equation (1): where nmis the molar value of SiNPs, T and Vmare the relaxation time (s) and molar volume of SiNPs (cm3 / mol), S represents the contact area between the active material and the electrolyte (cm3), AESis the steady-state potential change via the current pulse, and AEtis the potential change in a current pulse after subtracting IR drop. Calculated values of Du- for Si@PI@nano-TPA@E-350 and Si@PI@E-350 are presented in and Figure 9c. As shown in Figure 9c, the porous SnCh-doped CTC structured of Si@PI@nano-TPA@E-350 exhibited higher values of Du+ compared to less-porous CTC structured Si@PI-350. This result demonstrates that the combination of porosity and SnCh doping, brought about by the sublimation of TPA content of the electrode promotes the diffusion of lithium ions into / out of the electrode, thus improving the kinetics of charge transfer. Without wishing to be bound by theory, it is believed that the formation of porous SnCh-doped CTC structure in Si@PI@nano-TPA@E-350 not only improves the values of Du+, but also enhances the cycling stability and rate performance of the electrode (Figure 7d-7h) by providing free spaces in the integrated structure of the electrode, enabling the accommodation of volume changes involved in Li-ion insertion and extraction cycles.

[0228] Example 8 - Full-cell Li-ion examination

[0229] The structural stability and electrochemical properties Si@PI@nano-TPA@E-350 was further examined in a full -cell configuration using commercially available LiFePCU (LFP, Dynanonic) as the cathode and Si@PI@nano-TPA@E-350 as the anode. LFP is considered as a low-cost and stable cathode material, highly attractive for various applications including in electric vehicles.

[0230] Figure 9d shows the capacity matching diagram of the half-cells demonstrated by the charge-discharge curves of the two electrodes. The voltage window of LFP and Si@PI@nano-TPA@E-350 half-cells can be observed to be 4.2-2.5 V and 0.01-1.5 V, respectively. Therefore, full-cells were evaluated at a voltage window of 2.5-3.6 V, with the cathode to anode mass ratio of 8.5: 1 (N / P=1.5). The Si@PI@nano-TPA@E-350 electrode was pre-lithiated by conducting three activation cycles at 400 mA / g in half-cells, before being assembled into the full-cell. The galvanostatic charge-discharge curves of full-cell are presented in Figure 9e. The assembled full-cell delivered an initial reversible capacity of 154 mAh / g at 200 mA / g with an initial CE of 87.8% that rapidly increased to 97.4% in the second cycle, and reached an average of 99% for the next cycles. Unlike Li metal foil used in the half-cell configuration, the Li-ion source in at the full-cell was limited, hence the relatively high CE in the early cycles and excellent cycling stability of anodes suggest desirable practical performance of the resultant full- cell.

[0231] Figure 9f shows cyclic performance of the LiFePCL / / Si@PI@nano-TPA@E-350 full cell at 200 mA / g based on the combined masses of active materials at the cathode and the anode. According to Figure 9f, after 50 cycles, the discharge capacity was recorded at 150.6 mAh / g (retention rate ~ 97.8%) with an average coulombic efficiency of >99%. Furthermore, the correspondingly energy density was calculated to be 454.7 Wh / kg, which is highly desirable. Without wishing to be bound by theory, it is believed that this excellent cycling stability and relatively high energy density results from the structure which facilitates the Li- ions migration to Si and stabilizes the electrode structure.

[0232] The second-cycle galvanostatic charge-discharge profiles of the LFP cathode and the Si anode half-cells (Figure 9d), as well as those of the full cell (Figure 9e) are shown in Figure 9h. During the charging stage of the battery, a negative and positive potential was applied to the anode and the cathode, leading to Li insertion (anode) and Li extraction (cathode), respectively. As shown in Figure 9d, the GCD curve of the anode during Li insertion exhibited a sloping line between approximately 0.60 and 0.15 V, while the cathode GCD curve showed a plateau at around 3.50 V. Consequently, the GCD curve of the full cell during the charge period displayed a sloping line in the potential range of 3.25-3.45 V, influenced by the variable potential of the anode. With continued charging, the Si anode stabilized at approximately 0.1 V, while the cathode potential remained steady at around 3.5 V, resulting in a plateau in the full cell's GCD profile (Figure 9e). During the discharge process, the Si anode and LFP cathode experienced Li extraction and insertion, respectively. In this stage, the Si anode exhibited a slightly sloping Li extraction profile, while the LFP cathode showed a stable plateau (Figure 9d). However, the GCD curve of the full cell (Figure 9e) presents a relatively stable plateau, indicating that the Si anode provides a more stable GCD profile when combined with LFP, compared to its performance with Li foil in the halfcell configuration. As the cell discharge progressed further, a sloping GCD line was observed between approximately 3.30 and 2.90 V (Figure 9e), likely influenced by the sloping GCD profile of the Si anode at lower states of charge.

[0233] The full cell including the porous electrode and a second electrode containing LiFePC (LFP) exhibited the following second-cycle galvanostatic charge-discharge profiles: (a) during charging, the profile initially showed a sloping line within the potential range of 3.20 to 3.50 V, followed by a plateau at 3.5 ± 0.1 V; and (b) during discharging, the profile featured a plateau at 3.5 ± 0.1 V, followed by a sloping line within the potential range of 2.90 to 3.30 V.

[0234] According to Figure 9f, the discharge capacity of the full-cell was recorded at 150.6 mAh / g after 50 cycles, representing a capacity retention rate -97.8% with an average coulombic efficiency of >99%. Furthermore, the corresponding energy density of the cell was calculated to be 454.7 Wh / kg, which is highly desirable. The excellent cycling stability and high energy density of this electrode are believed to result from its structure, which facilitates Li-ion migration and stabilizes the electrode structure over cycling.

[0235] Example 9 - Morphological study of cycled electrodes

[0236] In order to further investigate the effect of SnCh decorated porous CTC structure enhanced with PI cross-linked binder on the Si anode, the surface morphologies of the Si@PI@nano-TPA@E-350 and Si@PI@E@350 electrodes at half-cell configuration before and after cycling were investigated by SEM. As shown in Figure 10a, the Si@PI@E@350 pristine electrode showed a very dense and smooth morphology, which is due to the formation of dense CTC structure within the PI chains, brought about by the heat-treatment applied at 350 °C. In contrast, as shown in Figure 10c, the pristine Si@PI@nano-TPA@E- 350 electrode exhibited a relatively porous structure, formed through the sublimation of the TPA component of the electrode during the annealing process. As shown in Figures 10b and lOd respectively, after 130 cycles of lithiation and delithiation at the current density of 800 mA / g, the surface of the Si@PI@E-350 electrode exhibited extensive cracks, with thickness of larger than 5 pm, while the Si@PI@nano-TPA@E-350 electrode shows considerably less extensive cracks with smaller thickness of 1-3 pm. Despite such cracks, the overall Si@PI@nano-TPA@E-350 electrode remained integrated, as shown in Figure lOd. The enhanced integrity of the electrode can be explained based on the formation of a porous CTC structure enhanced by the PI cross-linked binder, providing free spaces within the compact structure of the electrode, allowing the volume expansion / contraction of SiNPs during the cycling process without introducing major damage to the electrode. Despite the presence of CTC structure in the Si@PI@E-350 electrode, the extensive stress introduced by the volume expansion / contraction of SiNPs during cycling limits the performance of the binder system, disintegrating the electrode.

[0237] Other Embodiments

[0238] While certain embodiments have been disclosed above, the disclosure is not limited to such embodiments.

Claims

WHAT IS CLAIMED:

1. A method of processing a mixture comprising particles and a powder, the particles comprising a first compound, the powder comprising a second compound different from the first compound, the method comprising: heating the mixture to form a porous solid comprising the second compound, wherein the heating sublimates at least a portion of the first compound.

2. A method of processing a mixture comprising particles and a powder, the particles comprising a first compound, the powder comprising a second compound different from the first compound, the method comprising: heating the mixture to form a porous solid comprising the second compound, wherein: the heating removes at least a portion of the first compound; and the first compound comprises a member selected from the group consisting of: CXHY, where X and Y are a number from 1 to 16; CxHyOz, where X, Y and Z are a number from 1 to 16; and CxHyAz, where A is a halogen and where X, Y and Z are a number from 1 to 16.

3. The method of claim 2, wherein the removing at least a portion of the first compound comprises sublimating at least a portion of the first compound.

4. The method of any one of claims 1 to claim 3, further comprising: mixing the particles of the first compound and the powder of the second compound to form the mixture.

5. The method of claim 4, wherein mixing the particles of the first compound and the powder of the second compound comprises mechanically pressing the mixture.

6. The method of any one of claim 1 to claim 5, wherein the mixture comprises from 0.01 wt. % to 99.9 wt. % of the first compound, optionally from 1 wt. % to 80 wt. % of the first compound, optionally from 2 wt. % to 50 wt. % of the first compound, or optionally from 5 wt. % to 30 wt. % of the first compound.

7. The method of any one of claim 1 to claim 6, wherein the mixture comprises from 0.1 wt. % to 99.9 wt. % of the second compound, optionally from 10 wt. % to 99 wt. % of the second compound, optionally from 30 wt. % to 99 wt. % of the second compound, or optionally from 80 wt. % to 99 wt. % of the second compound.

8. The method of any one of claim 1 to claim 7, wherein the mixture is a powder.

9. The method of any one of claim 1 to claim 7, wherein the mixture is a slurry.

10. The method of any one of claim 1 to claim 9, wherein the mixture is heated to a temperature of from 70 °C to 500 °C, optionally to a temperature of from 150 °C to 400 °C, optionally to a temperature of from 200 °C to 400 °C, or optionally to a temperature of from 300 °C to 400 °C, to form the porous solid.

11. The method of any one of claim 1 to claim 10, wherein the mixture is heated at a pressure of from 1 mbar to 2026.5 mbar (2 atm), optionally a pressure of from 1 mbar to 1013.25 mbar (1 atm), to form the porous solid.

12. The method of any one of claim 1 to claim 11, wherein the mixture is heated for 1 second to 1 month, optionally for 10 seconds to 10 hours, optionally for 10 minutes to 5 hours, or optionally for 10 minutes to 2 hours, to form the porous solid.

13. The method of any one of claim 1 to claim 12, wherein the mixture is heated under an inert atmosphere, to form the porous solid.

14. The method of any one of claim 1 to claim 12, wherein the mixture is heated under an atmosphere comprising at least one member selected from the group consisting of air, oxygen, hydrogen, argon, helium, and nitrogen, to form the porous solid.

15. The method of any one of claim 1 to claim 12, wherein the mixture is heated under an atmosphere comprising at least one gas selected from the group consisting of oxygen, hydrogen, argon, helium, and nitrogen to form the porous solid.

16. The method of any one of claim 1 to claim 12, wherein the mixture is heated under an atmosphere comprising from 0 vol. % to 22 vol. % oxygen, optionally from 0 vol. % to 10 vol. % oxygen, optionally from 0 vol. % to 5 vol. % oxygen, or optionally from 0 vol. % to 0.1 vol. % oxygen, to form the porous solid.

17. A method of processing a mixture comprising a first compound and a second compound different from the first compound, the method comprising: reducing a pressure around the mixture to form a porous solid comprising the second compound, wherein reducing the pressure sublimates at least a portion of the first compound.

18. The method of claim 17, wherein the mixture further comprises a solvent and: reducing the pressure sublimates at least a portion of the solvent; and / or prior to reducing the pressure, a heat treatment is used to remove at least a portion of the solvent.

19. The method of claim 17 or claim 18, wherein the pressure is reduced to 100 mbar or less.

20. The method of claim 17 or claim 18, wherein reducing the pressure comprises applying a vacuum to the mixture.

21. The method of any one of claim 1 to claim 20, wherein: the first compound comprises CxHy, where X and Y are a number from 1 to 16, optionally where X and Y are a number from 1 to 10, optionally where X is a number from 7 to 14, and / or optionally where Y is a number from 4 to 16; the first compound comprises CxHyOz, where X, Y and Z are a number from 1 to 16, optionally where X, Y and Z are a number from 1 to 10, optionally where X is a number from 7 to 14, optionally where Y is a number from 4 to 16, and / or optionally where Z is a number from 1 to 4; or the first compound comprises CxHy Az, where A is a halogen, optionally where A is Cl, and where X, Y and Z are a number from 1 to 16, optionally where X, Y and Z are a number from 1 to 10, optionally where X is a number from 7 to 14, optionally where Y is anumber from 4 to 16, optionally where Z is a number from 1 to 4, and / or optionally where Z is a number from 1 to 2.

22. The method of any one of claim 1 to claim 20, wherein the first compound comprises at least one member selected from the group consisting of naphthalene, anthracene, benzoic acid, camphor, phthalic anhydride, para-dichlorobenzene and terephthalic acid.

23. The method of any one of claim 1 to claim 20, wherein the first compound comprises CsHeC .

24. The method of any one of claim 1 to claim 20, wherein the first compound comprises terephthalic acid.

25. The method of any one of claim 1 to claim 24, wherein, at atmospheric pressure, the first compound has a sublimation temperature of from 70 °C to 500 °C, optionally a sublimation temperature of from 200 °C to 500 °C, optionally a sublimation temperature of from 200 °C to 400 °C, or optionally a sublimation temperature of from 300 °C to 400 °C.

26. The method any one of claim 1 to claim 25, wherein the particles have a size of from 1 nm to 10 pm, optionally from 1 nm to 1 pm, optionally from 1 nm to 500 nm, or optionally from 1 nm to 100 nm.

27. The method any one of claim 1 to claim 25, wherein the particles have a largest linear dimension of from 1 nm to 10 pm, optionally from 1 pm to 1 mm, optionally from 1 pm to 200 pm, or optionally from 1 pm to 100 pm, from 100 nm to 10 pm, optionally from 500 nm to 10 pm, optionally from 100 nm to 1 pm, or optionally from 500 nm to 1 pm.

28. The method of any one of claim 1 to claim 27, wherein the mixture further comprises a metal-containing species.

29. The method of claim 28, wherein the porous solid comprises an oxide of the metalcontaining species.

30. The method of claim 28 or claim 29, wherein the metal -containing species comprises at least one member selected from the group consisting of a tin-containing species and a zinc- containing species.

31. The method of claim 28 or claim 29, wherein the metal -containing species comprises at least one member selected from the group consisting of tin chloride (SnCh) and tin oxide (SnO2).

32. The method of any one of claim 28 to claim 31, wherein the mixture comprises from 0.1 wt. % to 90 wt. % of the metal-containing species, optionally from 0.1 wt. % to 50 wt. % of the metal-containing species, or optionally from 0.1 wt. % to 20 wt. % of the metalcontaining species.

33. The method of any one of claim 28 to claim 32, wherein at least one of the following holds: the metal-containing species comprises a tin-containing species and the porous solid comprises particles comprising tin oxide; or the metal-containing species comprises a zinc-containing species and the porous solid comprises particles comprising zinc oxide.

34. The method of any one of claim 28 to claim 33, wherein heating the mixture forms a nanocrystalline metal oxide of the metal-containing species in the porous solid.

35. The method of any one of claim 28 to claim 34, wherein the porous solid comprises a nanocrystalline metal oxide of the metal-containing species.

36. The method of claim 35, wherein the nanocrystalline metal oxide have a particle size of from 1 nm to 50 nm, optionally from 1 nm to 10 nm, optionally from 2 nm to 20 nm, or optionally from 3 nm to 10 nm.

37. The method of any one of claim 1 to claim 36, wherein the second compound comprises at least one member selected from the group consisting of a polymer, a metal, ametal oxide, a semimetal, a ceramic, a monomer capable of polymerizing to form a polymer, graphite, glassy carbon, and a zinc-containing metal-organic framework.

38. The method of any one of claim 1 to claim 37, wherein the second compound comprises at least one member selected from the group consisting of a metal, a metal oxide, a semimetal, and a ceramic, and heating the mixture sinters the second compound.

39. The method of any one of claim 1 to claim 38, wherein the second compound comprises a polymer, and heating the mixture crosslinks the polymer.

40. The method of any one of claim 1 to claim 39, wherein the second compound comprises at least one polymer selected from the group consisting of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene (SBR), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), a polyurethane (PU), an acrylic-based polymer, and a polyimide (PI).

41. The method of any one of claim 1 to claim 40, wherein the second compound comprises a polymer, and the mixture further comprises a crosslinking agent.

42. The method of any one of claim 1 to claim 41, wherein the second compound comprises a member selected from the group consisting of silicon and a silicon oxide.

43. The method of any one of claim 1 to claim 42, wherein the second compound comprises a member selected from the group consisting of alumina, zirconia, calcium apatite, and a high entropy oxide.

44. The method of any one of claim 1 to claim 43, wherein the second compound comprises a member selected from the group consisting of LiFePCh, LiMnFePCU, LiCoCh, LiM CU, LiNiMnCoCh, LiNiCoAlCh, NaFePCU, and NaMnCh.

45. The method of any one of claim 1 to claim 44, wherein the second compound comprises a polyimide and silicon.

46. The method of any one of claim 1 to claim 45, wherein the mixture comprises a solvent, optionally wherein the solvent comprises a solvent selected from the group consisting of water and NMP.

47. The method of claim 46, wherein the mixture is coated onto a substrate and dried to remove the solvent, optionally wherein the substrate comprises a member selected from the group consisting of a copper substrate, an aluminium substrate, and a carbon substrate.

48. The method of any one of claim 1 to claim 47, wherein the porous solid comprises an average pore diameter of from 1 nm to 50 nm, optionally from 2 nm to 40 nm, or optionally from 10 nm to 30 nm.

49. The method of any one of claim 1 to claim 47, wherein the porous solid is microporous.

50. The method of any one of claim 1 to claim 47, wherein the porous solid is mesoporous.

51. The method of any one of claim 1 to claim 50, wherein the porous solid comprises a pore volume of from 0.05 cm3 / g to 0.5 cm3 / g, optionally from 0.7 cm3 / g to 0.4 cm3 / g, optionally from 0.06 cm3 / g to 0.4 cm3 / g, or optionally from 0.1 cm3 / g to 0.3 cm3 / g.

52. The method of any one of claim 1 or claim 3 to claim 51, further comprising condensing the sublimated first compound.

53. The method of claim 1 or claim 2, wherein: the first compound comprises terephalic acid; the particles have a size of from 1 nm to 100 nm; and the second compound comprises a polyimide and Si.

54. The method of any one of claim 1 to claim 52, further comprising manufacturing an electrode comprising the porous solid.

55. The method of claim 54, wherein: the electrode is an anode; or the electrode is a cathode.

56. The method of claim 55, further comprising making a battery comprising the electrode.

57. The method of claim 56, wherein the battery comprises a member selected from the group consisting of a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, and an aluminium-ion battery.

58. The method of claim 54, wherein the electrode has a Li-ion storage capacity of from 1000-3000 mAh / g, optionally from 1500-2800 mAh / g, or optionally from 1800-2500 mAh / g after 120 Li-ion insertion and extraction cycles at a current density of 200 mA / g.

59. The method of claim 54, wherein a full cell comprising the electrode and a second electrode comprising LiFePCU (LFP) having a discharge capacity of 150.6 mAh / g based on a mass of active materials at an anode and a cathode after 50 cycles with capacity retention rate of 97.8% has an average coulombic efficiency of at least 85 %, optionally at least 90 %, optionally at least 92 %, optionally at least 95 %, optionally at least 99 %, and / or optionally at most 100 %, optionally at most 99.9 %, at a current density of 800 mA / g.

60. The method of claim 54, wherein a full cell comprising the electrode and a second electrode comprising LiFePCh (LFP) comprises a gravimetric energy density of from 350 Wh / kg to 600 Wh / kg.

61. The method of claim 54, wherein: the first compound comprises terephalic acid; the particles have a size of from 1 nm to 100 nm; the second compound comprises a polyimide and Si; and the electrode comprises a Li-ion storage capacity of at least 2355mAh / g after 120 Li- ion insertion and extraction cycles at a current density of 200 mA / g.

62. The method of to claim 61, wherein: a Li-ion diffusion value of the electrode during a second-cycle lithiation process, in a haff cell configuration at room temperature and a current density of 200 mA / g, is in a range of IO'10 0- 10'13 5cm2 / s, optionally in a of range IO'10 0- IO'12 0cm2 / s; and / or the minimum Li-ion diffusion value of the electrode during a second-cycle delithiation process, in a half-cell configuration at room temperature and a current density of 200 mA / g, is 4 to 10 times higher than the minimum Li-ion diffusion value of an electrode fabricated without the addition of terephalic acid under the same conditions, optionally 30 to 40 times higher than that of an electrode fabricated without the addition of terephalic acid under the same conditions.

63. The method according to claim 61, a full cell comprising the electrode and a second electrode, the second electrode comprising LiFePCU (LFP), comprises a gravimetric energy density of from 350 Wh / kg to 600 Wh / kg, optionally wherein: a second-cycle galvanostatic charge profile of the full cell initially exhibits a sloping line within a potential range of 3.20 to 3.50 V, followed by a plateau at 3.5 ± 0.1 V; and / or a second-cycle galvanostatic discharge profile of the full cell initially exhibits a plateau at 3.5 ± 0.1 V, followed by a sloping line within the potential range of 2.90 to 3.30 V.

64. A composition comprising: a polymer stable at a temperature of at least 200 °C; and a compound selected from a metal, a metal oxide, a semimetal, and a ceramic, wherein the composition is porous.

65. The composition of claim 64, wherein the polymer is stable at a temperature of at least 250 °C, optionally at least 300 °C, optionally at least 350 °C, optionally at least 400 °C, optionally at least 450 °C, optionally at least 500 °C, optionally at least 550 °C, and / or optionally at most 600 °C.

66. The composition of claim 64 or claim 65, wherein the polymer comprises one or more polymers selected from the group consisting of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene (SBR), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), a polyurethane (PU), an acrylic-based polymer, and a polyimide (PI).

67. The composition of claim 64 or claim 65, wherein the polymer comprises a polyimide, optionally wherein the polyimide comprises a thermosetting polyimide, and / or optionally wherein the polyimide comprises a member selected from the group consisting of an aromatic polyimide, a semi -aromatic polyimide, and an aliphatic polyimide.

68. The composition of any one of claim 64 to claim 67, wherein the compound comprises a member selected from the group consisting of Si, SiO, SiCh, Fe2O3, FeO, FesC , P, SiP, SiP2, and Si3P69. The composition of claim 68, wherein the member comprises particles with particle sizes of 1 nm to 5 pm, optionally with particle sizes of 5 nm to 1 pm, or optionally with particle sizes of 10 nm to 200 nm.

70. The composition of any one of claim 64 to claim 69, wherein the compound comprises a member selected from the group consisting of semi -amorphous carbon, graphitic semi -spherical carbon particles, graphitic graphene nanosheets, and graphite powder.

71. The composition of any one of claim 64 to claim 70, wherein the compound comprises a member selected from the group consisting of LiFePCh, LiMnFePC , LiCoCh, LiMmC , LiNiMnCoCh, LiNiCoAlCh, NaFePC and NaMnCh.

72. The composition of any one of claim 64 to claim 71, wherein the composition further comprises metal oxide particles, optionally wherein the metal oxide particles comprise a member selected from the group consisting of tin oxide and zinc oxide, and / or optionally wherein the metal oxide particles are nanocrystalline.

73. The composition of any one of claim 64 to claim 72, wherein the composition comprises an average pore diameter of from 0.1 nm to 50 nm, optionally from 1 nm to 50 nm, optionally from 2 nm to 50 nm, optionally from 2 nm to 40 nm, or optionally from 10 nm to 30 nm.

74. The composition of any one of claim 64 to claim 72, wherein the composition is microporous.

75. The composition of any one of claim 64 to claim 72, wherein the composition is mesoporous.

76. The composition of any one of claim 64 to claim 75, wherein the composition comprises a pore volume of from 0.05 cm3 / g to 0.5 cm3 / g, optionally from 0.7 cm3 / g to 0.4 cm3 / g, optionally from 0.06 cm3 / g to 0.4 cm3 / g, or optionally from 0.1 cm3 / g to 0.3 cm3 / g.

77. An electrode comprising the composition of any one of claim 64 to claim 76.

78. The electrode of claim 77, wherein: the electrode is an anode; or the electrode is a cathode.

79. A battery, comprising the electrode of claim 77 or claim 78.

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