Production method and operating principle for pre-expanding chalcogenide-based electrodes

Abstract

The present invention relates to working principles and production processes for pre-expanding sulfur and / or other chalcogenides, and / or mixtures of any two or more. The invention also relates to an electrode / cathode comprising sulfur and / or a mixture of sulfur allotropes and / or a mixture of any two or more sulfur allotropes wherein the sulfur is pre-expanded in the form of photons / in the form of electrons / in the form of heat to a state in which it has a density comparable to that of metal sulfides. The expansion is performed prior to fabrication of the counter electrode / cathode to achieve an alkali metal and / or alkaline earth metal / ion battery. The resulting pre-expanded chalcogenide has, in addition to open / external pores, artificially generated internal cavities / pores, where the internal cavities limit and / or compensate for further expansion or partial / negligible expansion of sulfur during chemical / electrochemical reactions with monovalent, divalent, and trivalent metal ions.

Description

Technical Field

[0001] The present disclosure generally relates to the working principle and production method for volumetric pre-expansion of pure chalcogenides and / or doped chalcogenides (S, Se, Te, but not limited thereto) and / or mixtures of any two or more chalcogenides. The present disclosure also relates to an electrode / cathode that includes a chalcogenide pre-expanded volumetrically or more specifically sulfur (but not limited thereto), such as crystalline allotropes and / or glassy allotropes and / or amorphous allotropes and / or polymer (such as β-phase and / or γ-phase and / or ω-phase) allotropes and / or photonic sulfur allotropes and / or crystalline allotropes having a ring structure and / or mixtures of any two or more allotropes, wherein sulfur is pre-expanded or partially pre-expanded photonically / electrically / thermally to a state where it has a density comparable to that of metal sulfide, for example, the density of 1.66 g cm for Li2S -3 corresponds to 100% depth of discharge in a LiS battery.

[0002] The present disclosure also relates to a method and apparatus for pre-expanding chalcogenides (more preferably sulfur) and / or sulfur allotropes and mixtures with other chalcogenides (i.e., selenium, tellurium, etc.) to create internal cavities outside the already existing open pores, such that the contact of the internal cavities with the electrolyte is restricted and the internal cavities mainly serve as a buffer space for the volumetric expansion of discharge products for such an electrode / cathode during battery operation. The present disclosure also relates to an electrode / cathode that includes a pre-expanded chalcogenide (more preferably sulfur), and the present disclosure relates to a method for manufacturing such an electrode / cathode to achieve an electrochemical energy storage device and / or an alkali metal / alkaline earth metal / ion battery (such as a LiS battery, Na-S battery, Al-S battery, Mg-S battery, etc.) with an E / S ratio less than 1.5 ml g -1 . Background Art

[0003] Due to the severe energy and environmental crises and the rapid depletion of natural resources (i.e., fossil fuels), extensive investigations have been carried out to find efficient and environmentally friendly renewable energy sources. Lithium-sulfur (LiS) batteries have attracted attention due to their unprecedented theoretical capacity (1675 mAh g -1 ) and high energy density (2600 Wh kg -1) are rich in natural reserves, cost-effective, and environmentally sustainable, making them one of the most promising candidate materials for next-generation energy storage, and thus have been studied in depth. However, the use of LiS batteries is limited to niche applications, and the wider and industrial implementation of LiS technology is severely restricted by the following factors: the insulating nature of sulfur (electronic conductivity at room temperature is about 5X10 -30 Scm -1 ), the complex electrochemical reaction between S and Li (solid-state-liquid-state reaction) leading to the formation of lithium polysulfides (LPSs species: Li2S n , 4 ≤ n ≤ 8), LPS shuttling, parasitic growth of lithium dendrites, unstable solid electrolyte interface (SEI), poor cycle stability, and safety hazards leading to severe capacity decay or battery failure during cycling.

[0004] During discharge / charge, volume fluctuations occur within the positive and negative electrodes of an electrochemical unit cell. For example, during discharge, sulfur in the electrode / cathode expands due to the conversion reaction to form solid products (mainly lithium sulfide: Li2S or Li2S / Li2S2), while the metallic lithium anode shrinks due to the oxidation / stripping of lithium. The opposite process occurs during charge, where the lithium metal anode expands due to lithium plating. During charge / discharge, opposing actions (i.e., expansion and contraction) occur simultaneously. Due to chemical / electrochemical and / or redox reactions, taking sulfur and lithium sulfide as examples, the large volume fluctuations (about 79%) between the charge / discharge states result in insufficient utilization of sulfur, thus causing serious defects, poor cycle stability, and severe capacity decay. For example, in the case of Na-S batteries, the volume fluctuation is as high as about 152%, and similar behaviors have been reported for other monovalent, divalent, or trivalent metal ions (including Na, K, Ca, Mg, Al, Zn, etc.).

[0005] Regardless of the battery chemistry, the state-of-the-art slurry-based processes are widely used in the industry for manufacturing electrodes. This process is also used to prepare sulfur-containing cathodes for LiS batteries. However, the slurry-based processes have limitations, including the inability to produce complex electrode structures with customized and ordered pores, which are essential for effectively accommodating sulfur or metal sulfides (such as Li2S) during charging and discharging, while also providing space within the open pores to buffer the electrode thickness changes due to the volume fluctuations between the charging and discharging products. Additionally, the state-of-the-art slurry-based processes have a maximum porosity of approximately 45%. Any increase in porosity beyond this point can only be achieved by reducing the calendering pressure, which results in a low compaction density and excessive self-weight / volume inclusions that must be filled with electrolyte, leading to a loss of structural integrity, lower volumetric energy, and lower power density. Calendering is an important process / step in the production of an efficient current conduction path (network) within the cathode of the battery. This is achieved through the interaction of various particles (sulfur, binder, additives) in the slurry. The porosity of the cathode is also crucial for achieving a high-energy cathode. For example, the state-of-the-art cathodes can have a porosity of approximately 45%, which also allows for compensation of volume fluctuations (such as the 79% expansion and contraction of sulfur-based cathodes during charge and discharge cycles) and provides space for the electrolyte to occupy the internal voids of the cathode. For LiS batteries, charging (shrinkage) and discharging (expansion) also contribute to moving the electrolyte into and out of the electrode / cathode. Approximately 79% of the volume fluctuation is necessary to achieve the maximum (theoretically approximately 100%) utilization of sulfur, and then deliver a capacity of approximately 1675 mAh g -1 of the sulfur, which is the theoretical specific capacity of sulfur. However, in such slurry-based sulfur cathodes, the available space / volume for compensating the volume fluctuations during discharge is approximately 45%, which results in pore clogging. As a result, due to the clogged pores, most cathodes ultimately achieve a capacity of approximately 1100 mAh g -1 or lower at 1C. This is even more severe in NaS batteries because of the larger volume (approximately 152%) of the discharge product Na2S, resulting in an even lower utilization of the sulfur active material in the slurry-based cathodes. When lithiation or sodiation occurs, the expansion affects the pores and the expulsion of the electrolyte from the electrode / cathode, which significantly impacts the migration, diffusion, and convection processes in the electrochemical unit cell. The presence of electrolyte in the voids of the sulfur electrode / cathode is necessary to achieve efficient electrode kinetics and high sulfur utilization for obtaining a high-capacity electrode / positive electrode. For example, in an electrochemical cell, the density of sulfur changes from 2.07 g / cm 3 to 1.66 g / cm 3, resulting in the formation of solid Li2S in the fully discharged state. This equivalent density of sulfur can be achieved through pre-expansion and can compensate for the negative volume fluctuations within the LiS battery during unit cell operation. In metal chalcogenide batteries (such as LiS batteries), the sulfur-containing cathode undergoes constant expansion and contraction cycles. During this process, the movement of lithium ions and electrons (referred to as Li + / e - permeation) is established and restored simultaneously, while the components of the unit cell fragment and then reconstruct. In the long term, this process has a negative impact on various aspects of alkaline ion / sulfur batteries or LiS batteries.

[0006] In traditional slurry-based sulfur cathodes, sulfur is impregnated / encapsulated into a porous conductive matrix to accelerate electron transport, buffer volume expansion, and mitigate polysulfide dissolution. The porous conductive matrix can be, for example, porous carbon, graphene, carbon nanotubes, metal-organic frameworks, or a mixture of different conductive host structures, etc. And most importantly, sulfur is stabilized in the micro-meso-macro porous voids of the encapsulating structure. For example, traditional host structures based on carbon (such as carbide-derived carbon or CO2-etched carbon nanofibers) as described in US10,991,944B2 and porous 3D graphene scaffold structures as described in US11,335,911B2, where sulfur penetrates into a suitable host at the single particle level, where sulfur becomes part of the aggregates and eventually clusters. In most such slurry-based cathodes, sulfur presents as a crystalline phase, and the most stable crystal phase is, namely, orthorhombic sulfur. Alternative aspects can also be envisioned or realized, where the structural stabilization of sulfur is carried out, for example, stabilizing monoclinic sulfur (such as gamma sulfur (γ-sulfur)) within the cathode. This is achieved by providing a volume / void in the host structure where sulfur can enter and stabilize at a density of about 2.16 g cm -3 . Generally, the monoclinic γ-phase is metastable, but by capturing / confining γ-sulfur with a suitable host having engineered voids, due to the inability to expand in volume, the transformation from γ-sulfur to the stable orthorhombic α-phase with a lower density (about 2.07 g cm -3 ) will be impossible. Due to the density difference, the orthorhombic α-phase requires more space to expand volumetrically compared to the γ-phase. Nevertheless, despite some progress, the electrodes still suffer from poor electron conductivity, insufficient cycling performance, and low C-rate capabilities. SUMMARY OF THE INVENTION

[0007] The present disclosure also relates to a method for expanding a chalcogenide material, the method comprising steps a to e as follows:

[0008] a. Provide a chalcogenide material;

[0009] b. Coat at least one layer of graphene oxide on the chalcogenide material;

[0010] c. Immerse the coated chalcogenide material in a process liquid (and / or gas);

[0011] d. Subject the immersed and coated chalcogenide material to photon and / or electron radiation (specifically photon radiation) so as to raise the temperature of the chalcogenide material to a range of 320 °C to 420 °C, and more preferably, raise the temperature of the chalcogenide material to 365 °C, thereby causing the chalcogenide material to expand;

[0012] e. Quench the expanded chalcogenide material to a temperature range of -196 °C to 4 °C, preferably quench to below -35 °C, wherein the quenching medium is a process liquid and / or gas (specifically a process liquid).

[0013] The present disclosure also relates to an electrode (e.g., a cathode) comprising a chalcogenide material:

[0014] a) wherein the chalcogenide material has been expanded in a photon and / or electron and / or thermal manner to a state in which the chalcogenide material exhibits the same density state as the density state of the corresponding metal chalcogenide of the chalcogenide material;

[0015] b) wherein the apparent density of the chalcogenide material after expansion is within the range of the corresponding metal chalcogenide and the true density of the chalcogenide (e.g., the chalcogenide material) itself;

[0016] c) wherein the internal cavity of the chalcogenide material represents a buffer volume available for volume compensation during battery charging / discharging;

[0017] d) wherein the manufacturing process (e.g., the manufacturing process of the electrode) is characterized by, for example, the co - expansion of the chalcogenide material together with the process liquid and / or gas.

[0018] According to a non - limiting example, the true density can be understood as, for example, the density of a substance (e.g., a metal chalcogenide or a chalcogenide material) in a vacuum. It can be understood as being independent of external conditions such as buoyancy or gravity in air. In contrast, the apparent density of a substance can be specified, for example, by its weight per unit volume in air. In other words, the apparent density can be understood as, for example, an effective density taking into account voids and structural changes caused by cycling, while the true density can be understood as, for example, the theoretical density of the chalcogenide material (or metal chalcogenide) in a fully compacted, gap - free state.

[0019] According to a non - limiting example, the characteristics a) and d) of the electrode described above can be understood as referring to the electrode as manufactured. In other words, these characteristics can describe properties of the electrode that are generated by its manufacturing process and result in specific structural properties of the manufactured electrode (as also described in detail below).

[0020] According to a non - limiting example, characteristic b) can be understood as referring to the result of the manufacturing process, i.e., referring to the structure and properties of the manufactured electrode, and particularly to the apparent density of the chalcogenide material.

[0021] Similarly, according to a non - limiting example, characteristic c) can be understood as referring to the result of the manufacturing process, i.e., referring to the structure and properties of the manufactured electrode, and particularly to the internal cavity and its function in the operation of the electrode in the battery. Thus, all characteristics a) to d) can specify the electrode.

[0022] For example, according to characteristic a), sulfur (i.e., the chalcogenide material) can expand to a point where its density matches that of its metal chalcogenide, which means that sulfur has reached a swelling state similar to that of the lithium - sulfur compounds formed during discharge. This implies that sulfur in the cathode has expanded to a level where its structure becomes more porous, making its apparent density consistent with that of the lithium - sulfur compounds.

[0023] Furthermore, according to the example, characteristic b) can specify that after expansion, the apparent density of, for example, sulfur can be within the range of the true densities of both sulfur and polysulfide lithium. This range implies that the sulfur material is in a density state between its fully compacted form (true density of sulfur) and its chemically bonded state with lithium (true density of polysulfide lithium) after expansion.

[0024] According to a non - limiting example, the term "same density" can mean similar density, e.g., approximately similar density. The term equivalent density (as mentioned below) can mean "exactly the same density" or at least "the same density", as explained.

[0025] According to a non - limiting example, characteristics a) and b) can illustrate the difference between complete compensation and partial compensation of the volume expansion of the chalcogenide material (i.e., partial compensation due to closed pores, as explained in more detail below).

[0026] According to a non - limiting example, the internal cavity of characteristic c) can also be referred to as a closed pore / closed porosity.

[0027] According to non-limiting examples, the co-codilation mentioned in feature d) can particularly mean that the chalcogenide material and the process liquid and / or gas expand simultaneously (i.e., expand together) during manufacturing. Thus, the manufactured chalcogenide material can have several properties (as explained in more detail below) that would not exist if co-codilation were not applied. In particular, due to co-codilation, overheating, structural collapse, and evaporation of sulfur can be avoided. More specifically, the simultaneous expansion of the liquid / vapor can result in internal cavities (i.e., pores / voids). For example, gas can be present within the porous voids of a sulfur wafer. For example, the processing liquid can be converted to vapor and can cause the processing liquid to expand together with the vapor and gas inside the voids, thereby counteracting the expansion caused by photon-induced heating of the sulfur wafer. This instantaneous reaction prevents the structural collapse of the sulfur voids.

[0028] According to examples, a 2D material is used to cover the surface of the chalcogenide material, and / or a 2D material is used to coat the surface of the chalcogenide material, and / or the surface of the chalcogenide material is stabilized with a 2D material that cross-links with the chalcogenide during the expansion process. Preferably, the 2D material is a graphene-based material. For example, the graphene-based material is graphene oxide.

[0029] According to non-limiting examples, the chalcogenide material can be used as a redox-active material. The mass content of the chalcogenide material can be, for example, ≥85 wt%, and the chalcogenide material can exhibit hierarchical porosity. For example, the open pores can be used for the electrolyte / catholyte, while the closed pores can be used as a buffer volume for volume compensation.

[0030] According to examples, the chalcogenide material is selected from sulfur (S), selenium (Se), and tellurium (Te); in particular, the chalcogenide material is sulfur; more preferably, the chalcogenide material is a sulfur wafer (in particular a freestanding wafer).

[0031] According to non-limiting examples, the characteristic volume compensation for the discharge products can be distributed between the open pores and the closed pores. For example, the closed pores can have the ability to compensate for 0.25% to 100% of the total theoretical volume expansion of the electrochemical drive (e.g., the volume expansion from sulfur to Li2S corresponds to 79%). The open pores can compensate for the remaining 0% to 50% of the total volume change of the discharged metal disulfide product.

[0032] In another example, the end product of the fully discharged state can be Na2S, and the volume compensation can be partially covered by the combined part of the available closed pores (e.g., ≤90%) of the sulfur wafer and the open pores (e.g., ≤45%) available for the electrolyte. The last 22% of the theoretical 157% conversion from sulfur to Na2S may not be compensated. Therefore, the volume fluctuation of such a battery cell may be limited to (i.e., restricted to) 22% (i.e., 157% to 135%).

[0033] The electrode may be restricted within an operating window (e.g., when used as the cathode of a battery). For example, the end product of discharge may be limited to Na2S2 and the volume fluctuation of its theory of 67% can be completely covered by the closed pores.

[0034] The present disclosure also relates to a laser-based device for expanding and quenching a chalcogenide material to a state in which the chalcogenide material has a density comparable to that of a metal chalcogenide.

[0035] According to an example, the wavelength of the photon is between 430 nm and 100 nm, preferably, the wavelength of the photon is 430 nm to 254 nm, and more preferably, the wavelength of the photon is 390 nm.

[0036] The present disclosure also relates to a FLA / IPL (flash lamp annealing (FLA) / intense pulsed light (IPL))-based device for expanding and quenching a chalcogenide material to a state in which the chalcogenide material has a density comparable to that of a metal chalcogenide. The FLA / IPL-based device (i.e., the FLA / IPL source) may include or use a xenon lamp, which may be part of, for example, a xenon flash lamp assembly. For example, the intensity of the FLA may be higher than the intensity of the IPL.

[0037] According to an example, the wavelength of the photon is between 800 nm and 170 nm, and more preferably, the wavelength of the photon is in the range of 450 nm to 250 nm.

[0038] According to an example, the FLA / IPL source generates a high-intensity photon flux having a fluence of 25 J / cm 2 or higher, preferably 120 J / cm 2 or more.

[0039] According to an example, the laser source generates a high-intensity photon flux having a fluence in the range of 100 J / cm 2 to 400 J / cm 2 or more preferably 250 J / cm 2 or more.

[0040] According to the example, the laser beam is guided through the processing liquid / quenching liquid.

[0041] The present disclosure also relates to an electrode (in particular, a cathode) comprising an expanded chalcogenide material prepared according to the method described above (e.g., Example 3 or Example 4).

[0042] The present disclosure also relates to a battery comprising an electrode (in particular, a cathode) as described above.

[0043] According to the example, the electrolyte-to-sulfur (E / S) ratio of the battery is less than 1.99 ml / g.

[0044] The present disclosure also relates to a device for performing the method described above, the device comprising:

[0045] - a chamber for placing a wafer comprising a chalcogenide material (in particular, a wafer comprising sulfur);

[0046] - a radiation source for photonically expanding the chalcogenide (in particular, sulfur); and

[0047] - a control system for regulating the expansion process.

[0048] The device may further comprise:

[0049] - a movable arm carrying the radiation source (in particular a laser source), and the movable arm comprising means for providing a liquid flow to the wafer; and

[0050] - a holding device for the wafer, the holding device having a rotation function and being capable of rotating in a clockwise direction and / or a counterclockwise direction at a desired speed (preferably 15 to 20 revolutions per minute).

[0051] According to the example, the expanded chalcogenide material (in particular, expanded sulfur) has a density lower than 1.70 g / cm 3 (such as 1.66 g / cm 3 )

[0052] According to the example, the photon radiation is performed with a laser; in particular, the photon radiation is performed with an FLA laser source, a UV laser source, or an IPL laser source.

[0053] According to the example, the FLA laser source, the UV laser source, or the IPL laser source has a high-intensity photon flux with a fluence of 25 J / cm 2 or higher, preferably 120 J / cm 2 or more.

[0054] According to the example, steps d and e are carried out simultaneously.

[0055] According to the example, the liquid is selected from water, fluorides, ethanol, CO2, and isopropanol, or any mixture thereof.

[0056] The term "chalcogenide material" refers to a material that includes a chalcogenide or a mixture of two or more chalcogenides. The term "chalcogenide material" also refers to pure chalcogenides and / or doped chalcogenides. In addition, the term "chalcogenide material" refers to chalcogenide allotropes, such as crystalline allotropes with a tadpole-shaped structure and / or glassy allotropes and / or amorphous allotropes and / or polymeric (e.g., β-phase and / or γ-phase and / or ω-phase) allotropes and / or photothio allotropes and / or crystalline allotropes with a ring structure and / or any mixture of two or more allotropes. Preferably, the chalcogenide is selected from sulfur (S), selenium (Se), and tellurium (Te); particularly preferably, the chalcogenide material is sulfur. Preferably, the chalcogenide material is a chalcogenide wafer; particularly, the chalcogenide material is a sulfur wafer. Further preferably, the wafer is a free-standing wafer.

[0057] The term "swelling" refers to a situation where the actual size of a material changes. Preferably, the swelling is thermal swelling. According to a preferred example, the chalcogenide material (particularly, sulfur) swells due to a chemical / electrochemical and / or redox reaction (e.g., lithiation and / or sodiation, etc.) with a monovalent, divalent, or trivalent metal ion (such as Li + 、Na + 、K + 、Ca 2+ 、Mg 2+ 、Al 3+ 、Zn 2+ etc.) to a state where it will not further swell or will only swell partially or the swelling is negligible. In the context of the present disclosure, swelling to such a state is referred to as "pre-swelling" or "after pre-swelling".

[0058] The process liquid is preferably selected from water, fluorides (fluorinert), ethanol, CO2, and isopropanol, or any mixture thereof. The process liquid may or may not be gas-saturated.

[0059] According to the present disclosure, the photon radiation or optical radiation is preferably carried out with a laser; particularly, the photon radiation or optical radiation is carried out with an FLA laser source, a UV laser source, or an IPL laser source.

[0060] Additional exemplary aspects of the present disclosure relate to an electrode / cathode that includes a chalcogenide-based active material, and more preferably the electrode / cathode includes sulfur that has been pre-expanded photonically to a density comparable to that of a metal sulfide (such as Li2S). The pre-expansion is performed before using sulfur in the manufacture of the electrode / cathode to achieve an alkali metal or alkaline earth metal / ion battery (such as a LiS battery). The pre-expansion of sulfur is achieved by tailoring the expansion process by taking advantage of the high thermal volume expansion coefficient of sulfur. This pre-expansion ensures that sulfur will not further expand or will expand negligibly during the chemical / electrochemical and / or redox reactions (such as lithiation and / or sodiation) that occur during battery charging and discharging.

[0061] Another exemplary aspect relates to an electrode / cathode that includes a mixture of chalcogenide allotropes, and more preferably includes sulfur allotropes having a crystalline phase, a glassy phase, an amorphous phase, and a polymeric phase (such as β-phase sulfur, γ-phase sulfur, and ω-phase sulfur). Sulfur has been pre-expanded photonically / electronically / thermally to a density comparable to that of a metal sulfide (such as Li2S) before being used in the manufacture of the electrode / cathode to achieve an alkali metal or alkaline earth metal / ion battery (such as a LiS battery). The pre-expansion of pure sulfur and doped sulfur and / or other chalcogenides and / or mixtures thereof is achieved by tailoring the expansion process by taking advantage of the high thermal volume expansion coefficient. This pre-expansion ensures that pure sulfur and doped sulfur and / or other chalcogenides will not further expand or will expand negligibly during the chemical / electrochemical and / or redox reactions (such as lithiation and / or sodiation) that occur during battery charging and discharging.

[0062] In another exemplary aspect, the electrode / cathode includes a mixture of chalcogenides (including sulfur, selenium, and tellurium) that have been pre-expanded photonically / electronically / thermally to a density comparable to that of a metal sulfide. The pre-expansion is performed before using the mixture of chalcogenides in the manufacture of the electrode / cathode to achieve an alkali metal or alkaline earth metal / ion battery (such as a LiS battery). The pre-expansion of the chalcogenide mixture is achieved by tailoring the expansion process by using the unusually high thermal volume expansion coefficient of the chalcogenides. This pre-expansion ensures that the chalcogenide mixture will not further expand or will expand negligibly during the chemical / electrochemical and / or redox reactions (such as lithiation and / or sodiation) that occur during battery charging and discharging.

[0063] Another exemplary aspect of the present disclosure relates to methods and apparatuses for pre-expanding sulfur and / or other chalcogenides (including selenium, tellurium), and / or mixtures of any two or more chalcogenides. The pre-expansion is carried out, for example, by using a laser or other high-energy light source to induce heating in a photon / electron / thermal manner. The resulting pre-expanded sulfur and / or chalcogenides can then be used in electrode / cathode fabrication to enable alkali metal or alkaline earth metal / ion batteries (such as LiS batteries). The pre-expansion ensures that sulfur and / or chalcogenides will not further expand or expand negligibly during chemical / electrochemical and / or redox reactions (such as lithiation and / or sodiation) that occur during charging.

[0064] Another exemplary aspect of the present disclosure relates to electrodes / cathodes made from mixtures of sulfur and / or sulfur allotropes (such as crystalline sulfur, glassy sulfur, amorphous sulfur, or polymeric sulfur), which have been pre-expanded in a photon / electron / thermal manner to a density comparable to that of metal sulfides (such as Li2S). The pre-expanded mixture of sulfur and / or sulfur allotropes can then be used to fabricate electrodes / cathodes for alkali metal or alkaline earth metal / ion batteries (such as LiS batteries).

[0065] Another exemplary aspect of the present disclosure relates to a method of using photon energy or thermal energy to pre-expand sulfur and / or other chalcogenides (such as selenium or tellurium) to achieve a density comparable to that of metal sulfides. The pre-expanded mixture of sulfur and / or chalcogenides can then be used to fabricate electrodes / cathodes for alkali metal or alkaline earth metal / ion batteries (such as LiS batteries).

[0066] Another exemplary aspect of the present disclosure is an apparatus for using photon energy or thermal energy to pre-expand sulfur and / or other chalcogenides. The apparatus includes: a chamber for containing sulfur and / or chalcogenides; and a photon energy or thermal energy source for expanding sulfur and / or chalcogenides to a desired density. The pre-expanded mixture of sulfur and / or chalcogenides can then be used to fabricate electrodes / cathodes for alkali metal or alkaline earth metal / ion batteries (such as LiS batteries).

[0067] In additional examples, the present disclosure relates to an electrode / cathode that includes sulfur and / or a combination of different sulfur allotropes, the different allotropes including crystalline, glassy, amorphous, and polymeric forms (such as β-phase sulfur, γ-phase sulfur, and ω-phase sulfur). The electrode / cathode is designed for use in alkali metal and / or alkaline earth metal / ion batteries (specifically LiS batteries). Before the mixture of sulfur and / or sulfur allotropes is used, it is pre-expanded in the form of photons / thermally to a density comparable to that of a metal sulfide (such as the final product Li2S of a fully discharged LiS battery). The pre-expansion of sulfur is achieved by using sulfur's unusually high coefficient of thermal volume expansion. This allows for the customized pre-expansion of sulfur and other chalcogenides (such as selenium and tellurium) and combinations of these materials. The pre-expansion ensures that sulfur will not further expand or will only expand negligibly due to chemical / electrochemical and / or redox reactions with metal ions (such as Li, Na, K, Ca, Mg, Al, and Zn). In addition to the electrode / cathode, the present disclosure also relates to methods and apparatuses for pre-expanding sulfur and other chalcogenides. This allows for the efficient and consistent production of electrodes / cathodes for LiS batteries and other metal / ion batteries.

[0068] In additional examples, the present disclosure also relates to an electrode / cathode that includes a mixture of sulfur and / or sulfur allotropes and a mixture of any two or more of these allotropes, such as crystalline sulfur, glassy sulfur, amorphous sulfur, or polymeric sulfur. Such an electrode / cathode is designed for use in alkali metal and / or alkaline earth metal / ion batteries (specifically LiS batteries). Before use, sulfur undergoes a pre-expansion process in which it is expanded in a photon or thermal manner to a density comparable to that of a metal sulfide (such as Li2S). This pre-expansion is achieved by sulfur's unusually high coefficient of thermal volume expansion. By pre-expanding sulfur, it can expand negligibly or not at all during battery operation due to chemical or electrochemical reactions (such as lithiation or sodiation). The present disclosure also includes methods and apparatuses for pre-expanding sulfur and other chalcogenides (such as selenium and tellurium), and mixtures of any two or more of these elements. The pre-expanded mixture of sulfur and / or sulfur allotropes can then be used to fabricate electrodes / cathodes for alkali metal and / or alkaline earth metal / ion batteries.

[0069] In another example, the present disclosure also relates to a novel electrode / cathode for use in lithium-sulfur batteries and other types of alkali metal or alkaline earth metal / ion batteries. The electrode / cathode is made of a mixture of sulfur and / or different sulfur allotropes, such as crystalline sulfur, vitreous sulfur, amorphous sulfur, or polymeric sulfur. These materials are pre-expanded by a process of heating them either photonically or thermally, such that these materials have a density comparable to that of metal sulfides (such as Li2S). This pre-expansion process occurs before the sulfur and / or sulfur allotropes are used to fabricate the electrode / cathode. One of the unique features of the present disclosure is the customization of the pre-expansion process by taking advantage of the unusually high thermal volume expansion coefficient of sulfur. This allows sulfur and / or other chalcogenides (such as selenium or tellurium) to be pre-expanded to a state where they will not further expand or will expand negligibly during the operation of the battery due to chemical or electrochemical reactions (such as lithiation or sodiation). The present disclosure also relates to methods and apparatus for pre-expanding sulfur and / or other chalcogenides. This includes the design and construction of apparatus for heating the materials either photonically or thermally to the desired density and the use of such apparatus in the process. Overall, the use of pre-expanded sulfur and / or sulfur allotropes in the electrodes / cathodes of lithium-sulfur batteries or other metal / ion batteries has the potential to improve the performance and durability of these batteries, as well as to increase their energy density.

[0070] In another example, the present disclosure relates to an electrode / cathode comprising a mixture of sulfur and / or sulfur allotropes, such as crystalline sulfur, vitreous sulfur, amorphous sulfur, or polymeric sulfur, for use in alkali metal and / or alkaline earth metal / ion batteries (such as LiS batteries). In some examples, a method of pre-expanding sulfur either photonically / thermally to have a density comparable to that of metal sulfides (such as Li2S in the case of a fully discharged LiS battery). The pre-expansion is carried out before the sulfur is used in the electrode / cathode, and the resulting pre-expanded sulfur has the advantage of not further expanding or expanding negligibly due to chemical / electrochemical reactions (such as lithiation or sodiation) with monovalent, divalent, or trivalent metal ions. In some examples, sulfur can be mixed with one or more other chalcogenides (such as selenium or tellurium) to further improve the performance of the electrode / cathode. The present disclosure also relates to methods and apparatus for the pre-expansion of sulfur and / or other chalcogenides.

[0071] The present disclosure has the following advantages:

[0072] a. The use of pre-expanded sulfur in the electrode / cathode can significantly improve the performance of alkali metal and / or alkaline earth metal / ion batteries (such as LiS batteries), thereby increasing material utilization, reducing capacity fade, and extending cycle life.

[0073] b. Methods and apparatuses for pre-expanding sulfur and / or other chalcogenides can be easily implemented and scaled up for industrial production.

[0074] c. The present disclosure provides a simple and cost-effective method to overcome the challenges posed by the extremely high thermal volume expansion coefficients of sulfur and other chalcogenides. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 : Coefficients of linear and volumetric thermal expansion of different metals.

[0076] Figure 2 : This chart presents the relationship between sulfur density and temperature.

[0077] Figure 3 : Parameters affecting the energy density of LiS batteries, including the electrolyte-to-sulfur ratio. (Reference: https: / / doi.org / 10.1007 / s41918-018-0010-3).

[0078] Figure 4(a): Schematic diagram (isometric view) of an apparatus for sequential expansion of chalcogenide materials or more specifically sulfur wafers. The apparatus includes a chamber 401 for accommodating a rotating mixture of sulfur wafers and / or sulfur allotropes and expansion compensation wafer holder pins 402 presented within a wafer holder 403; a radiation source 405 for photonically / thermally expanding the mixture of sulfur and / or sulfur allotropes, the radiation source 405 further including a cooling liquid 404 supplied via a supply pipe for a process liquid 406 to a cooling head; an arm / driver 407 for supporting the movement of a laser source in the x, y, and z directions as well as angular rotation and tilting; an actuator 408 for wafer rotation; and the entire body 409 of the apparatus. A control system for regulating the expansion process to achieve the desired density of the pre-expanded mixture of sulfur and / or sulfur allotropes. *Not to scale.

[0079] Figure 4(b): Schematic diagram (top view) of an apparatus for sequential expansion with a sulfur wafer. *Not to scale.

[0080] Figure 5: Schematic diagram (side view) of an apparatus for pre-expanding a chalcogenide material or more specifically a sulfur wafer assisted by nanobubbles. The apparatus includes a generator 501, a rack 502, and a wafer holder 504. The generator 501 is capable of generating nanobubbles. The rack 502 is capable of accommodating a chalcogenide wafer 503. The wafer holder 504 is capable of causing volumetric expansion of the chalcogenide wafer. The assembly is immersed in a cooling liquid / process liquid 505. The apparatus also includes a radiation guiding crystal 506 that focuses photons from a source 507, such as a xenon lamp that is part of a xenon flash lamp assembly 508. The apparatus also includes a lamp holder 509. The double jacket device includes an outer wall 511, an inner wall 512, and an aao film 510, as shown in the schematic diagram. *Not to scale.

[0081] Figure 6 : Simplified schematic diagram of a sulfur wafer growth apparatus, where the apparatus includes a chamber 601 that houses a mother liquid 602; a wafer holder 603; and a grown sulfur wafer 604 *Not to scale.

[0082] Figure 7 : Simplified schematic diagram of a pre-expansion process, where the grown sulfur wafer 604 includes aligned seeds that also act as an electron-permeable network 701 on which sulfur crystals 702 grow and are coated with one or more graphene oxide layers 703. The seeds are immersed in a process liquid 704 at room temperature. Then, the grown sulfur wafer is subjected to a pre-expansion process, where the temperature of the chalcogenide wafer is increased to 420 °C, resulting in the expansion of the chalcogenide 702 within the wafer and the reduction of GO, i.e., the formation of rGO 705. After quenching the pre-expanded sulfur wafer, contraction of the chalcogenide occurs, resulting in the formation of internal cavities 706 within the wafer due to the contraction of the chalcogenide towards rGO, which acts as a structural stabilizing layer. *Not to scale.

[0083] Figure 8 : The figure shows the volumetric expansion during the electrochemical reaction of sulfur with alkaline ions (i.e., Li and Na) and the subsequent compensation for the volumetric expansion between open pores and closed pores. Detailed Description

[0084] The present disclosure will be described in more detail below based on several non-limiting examples, as schematically illustrated in the accompanying drawings.

[0085] To overcome the problems of traditional technologies, as explained at the beginning of the present disclosure, in the present disclosure, a sulfur cathode (before its use in an alkaline ion / sulfur battery) is expanded in a photon-based manner / in an electron-based manner / in a thermal-based manner to a state where its density is similar to that of Li2S (the product of a fully discharged LiS battery), and the sulfur cathode is crosslinked with a 2D material such as GO. After sulfur expansion, due to the deoxygenation of GO, the 2D material reacts with sulfur to form reduced graphene oxide (rGO), and at the same time, the 2D material and sulfur radicals at the phase interface between GO and sulfur are crosslinked. Sulfur has an unusually high linear and volumetric thermal expansion coefficient (presented in Figure 1 ), and thus is advantageously used to customize the expansion of sulfur. During expansion and crosslinking, rGO serves as a shell and also as a mechanical support, thereby inducing sulfur contraction when cooling from the core centered on sulfur towards the shell. ( Figure 6 , for visualization of the contraction, the core towards the shell and also towards the sulfur chains). Figure 2 Represents the relationship between the density of sulfur and temperature.

[0086] In principle, pre-expansion means that sulfur will not expand further or will expand partially or negligibly due to chemical / electrochemical and / or redox reactions (such as lithiation and / or sodiation, etc.) with monovalent, divalent, or trivalent metal ions (such as Li + , Na + , K + , Ca 2+ , Mg 2+ , Al 3+ , Zn 2+ , etc.).

[0087] Another aspect of a successful lithium-sulfur battery is the specific ratio of electrolyte to sulfur, in units of milliliters per gram (ml g -1 ). State-of-the-art LiS batteries typically use an E / S ratio of about 5 ml g -1 . This ratio is a key factor determining the commercial viability of the battery, as shown in Figure 3 . It is important to carefully consider the E / S ratio when designing and evaluating LiS batteries.

[0088] The present disclosure relates to an apparatus and method for pre-expanding chalcogenides (S, Se, Te) and / or mixtures of any two or more (but not limited thereto) or more specifically pure sulfur and / or doped sulfur or more specifically sulfur wafers (EP 3913705 A1) (but not limited thereto). The pre-expansion can be carried out in various ways. For the present application, we preferably propose for the first time two unique methods, namely: 1. flash expansion and 2. sequential expansion. The present disclosure also relates to an electrode / cathode comprising a pre-expanded chalcogenide or more specifically a mixture of sulfur and / or sulfur allotropes, wherein sulfur is pre-expanded in a photon / thermal manner to a state where it has a density comparable to that of metal sulfides. Generally speaking, in this process, incident photons / electrons and / or heat treatment cause the expansion of sulfur, which is due to a local temperature increase within sulfur, resulting in an increase in volume, which is due to the high volume expansion coefficient of sulfur, where the density of sulfur decreases from 2.08 g / cm 3 to 1.66 g / cm 3 , and subsequently sulfur undergoes ROP, and sulfur then crosslinks with 2D materials such as GO, thereby forming a strong outer shell. When cooled to room temperature, the robustness of the crosslinked GO layer at the GO / sulfur phase interface prevents the resulting sulfur coating from shrinking from the shell to the core, but facilitates the inward shrinkage of sulfur from the core to the shell, which in turn generates an internal cavity, as shown in Figure 6 .

[0089] Before pre-expansion, one or more thin layers of 2D materials that are sufficiently transparent to the UV spectrum can bond with chalcogenide-based materials (more preferably sulfur), while providing high electronic conductivity for redox operations and permeability towards charge carrier ions (such as graphene oxide, etc.). By dip coating / vacuum filtration / spray coating / spin coating / rod coating / slot coating / roll-to-roll printing / screen printing / flexographic printing / lithographic printing / inkjet printing / film stretching, or more preferably by electrostatically driven layer-by-layer (LbL) assembly, or more preferably by dipping a wafer into a liquid dispersion of 2D materials, the one or more thin layers will be coated on the electrode / cathode, which includes crystalline sulfur, vitreous sulfur, amorphous sulfur, and / or polymers (such as β-phase, γ-phase, and / or ω-phase) sulfur and / or mixtures of any two or more sulfur allotropes (such as porous sulfur wafers (EP 3913705 A1)), and then IR / air drying is carried out. During this process, the nanosheets of 2D materials or more preferably GO are electrostatically attached to the chalcogenide-based wafer, more preferably to the surface of the sulfur wafer. The process of LbL coating (i.e., dipping / emerging) and drying is repeated several times until the desired thickness of the 2D material is achieved on the porous wafer (the thickness ranges from 5 nm to 50 nm, or more preferably the thickness is 20 nm, or more preferably the thickness is 10 nm).

[0090] As a result of the pre-expansion process, the resulting sulfur electrode includes two types of pores, i) open pores that originate from the wafer growth of a chalcogenide-based cathode as described in EP 3913705 A1 and that are available for charge carriers in the electrolyte; and ii) internal cavities that originate from the photon beam / electron beam and / or thermally induced expansion of sulfur and its subsequent crosslinking with the 2D material shell, which enhances the structural stability of the sulfur wafer in the post-pre-expansion state, such that upon cooling to room temperature or even lower temperatures, internal cavities are formed due to the inward volume contraction of sulfur (i.e., the core towards the shell). The newly formed internal cavities not only provide a volume buffering space for the discharge products, namely metal disulfides (more preferably lithium disulfide, Li2S), but also increase the redox active specific surface area between the active material and the charge carriers in the electrolyte. After successful pre-expansion, chalcogenides or more specifically sulfur can be used for electrode / cathode fabrication to enable alkali metal and / or alkaline earth (Li, Na, K, Ca, Mg, Al, Zn, etc.) metal / ion or more specifically LiS batteries. In principle, pre-expansion means that sulfur will not expand further or the expansion is negligible or partial, where the upper limit of the volume fluctuation compensation provided by this method is limited by the boiling point of sulfur at 1 atmosphere (about 444 °C), and an extension beyond this operating window can be provided by applying a pressure higher than 1 atmosphere to change the boiling point of sulfur to a higher temperature. The present disclosure benefits from the unusually high thermal linear / volume expansion coefficient of sulfur ( Figure 1 ), which is used to set the pre-expansion and is similarly applicable to other pure chalcogenides and doped chalcogenides (such as Se, Te, etc.), and / or any mixture of two or more of them.

[0091] Method 1. Sequential expansion: The apparatus for sequential expansion is presented in Figures 4(a) to 4(b) . The apparatus includes a metal / glass body that includes an adjustable / movable FLA / UV / IPL laser source with a concentrated cooling liquid / water flow, which is attached to the top of the apparatus as shown in FIG. 4(a). The movable FLA / UV / IPL laser source serves as a writing head that is capable of writing a defined / programmable pattern on the wafer. The FLA / UV / IPL laser source is capable of generating with 25 J / cm 2 , preferably 120 J / cm 2A high-intensity photon flux of the above-mentioned fluence is sufficient to expand chalcogenides and / or any mixture of two or more chalcogenides, or more specifically pure sulfur and / or doped sulfur (but not limited to this). The device is also equipped with a sample / wafer holder having a rotation function, as presented in Figure 4(b). The sample holder can be rotated in a clockwise direction and / or counterclockwise direction at a desired speed (preferably 15 to 20 revolutions per minute). A cold-quenched liquid stream flows centered on the FLA / UV / IPL laser beam to quench the heated / melted sulfur and minimize the risk of wafer collapse. A suitable processing liquid capable of instant heat exchange can be used in the stream, for example, water or ethanol or CO2 or IPA, or any mixture of two or more. The temperature of the processing liquid is maintained between -110 °C and +4 °C, and the temperature of the processing liquid is controlled by means of a heat exchanger. The device may also include an auxiliary channel / may not include an auxiliary channel, which sprays the processing liquid / coolant liquid to cool the sample / wafer from the opposite side of the sample / wafer holder during the pre-expansion process while protecting the structure from collapse.

[0092] Principle of operation: Pre-expansion of pure chalcogenides and / or doped chalcogenides and / or any mixture of two or more (but not limited to this) can be carried out by a sequential expansion method. For example, pre-expansion of a self-standing layered porous monolithic sulfur wafer (EP3913705 A1) can be carried out by a flash expansion method. Different from the flash expansion method that exposes the entire wafer to light simultaneously, the sequential expansion method operates based on the principle of point heating and quenching. During this process, a self-standing porous monolithic sulfur wafer (EP 3913705A1) is placed in a sample / wafer holder, as described in Figure 4(b). The FLA / UV / IPL laser source / radiation source emits a high-intensity photon flux (25 J / cm 2 to 120 J / cm 2 between) to the sulfur wafer. Incident photons from the FLA / UV / IPL source are absorbed by the sulfur wafer, resulting in local heating, expansion, and ring-opening polymerization (ROP). The processing liquid stream immediately quenches the polymerized sulfur and the processing liquid stream helps to inhibit the wafer structure. During this process, the temperature of the processing liquid is maintained between -110 °C and +4 °C to avoid overheating, structure collapse, and vaporization of sulfur.

[0093] Method 2: Pre-expansion supported by nanobubbles: The device for pre-expansion supported by nanobubbles is presented in Figure 5 In it. The device includes a system of enclosed metal / glass containers, which is equipped with an FLA / UV / IPL laser source at the top. The FLA / UV / IPL laser source is adapted to generate a photon flux with 25 J / cm 2 、preferably 120 J / cm 2A high-intensity photon flux of the above fluence, which is suitable for swelling chalcogenides and / or a mixture of any two or more chalcogenides, or more specifically pure sulfur and / or doped sulfur (but not limited thereto), or more preferably a sulfur wafer (EP 3913705 A1). The laser source also includes a focusing lens that directly transfers the incident photons from the FLA / UV / IPL laser source to the sulfur wafer, and the focusing lens can be partially immersed in the process liquid or may not be immersed in the process liquid to enhance the intensity of the photons incident on the wafer by moderating through the principle of refraction / reflection of photons. The metal / glass container is a jacketed container with a vacuum between its inner and outer containers, such that the inner wall of the outer container can be coated with a reflective coating for photons, such as barium sulfate, thereby allowing the photons to be totally reflected and focused towards the sulfur wafer. In addition, since there is a vacuum between the outer and inner containers, the heat / mass transfer with the external system is suppressed. The FLA / UV / IPL laser source is adapted to generate a high-intensity photon flux with a fluence of 25 J / cm 2 , preferably 120 J / cm 2 or above, which is suitable for swelling chalcogenides and / or a mixture of any two or more chalcogenides, or more specifically pure sulfur and / or doped sulfur (but not limited thereto), or more preferably a sulfur wafer (EP 3913705 A1). The apparatus also includes a wafer holder that can be immersed in the process liquid (water or fluorine inert gas or ethanol or CO2 or IPA, and / or any mixture of two or more thereof), which can dissipate heat from the sulfur wafer during irradiation. The apparatus also includes a generator disk fixed at the bottom of the container through which a gas of an appropriate mixture (such as CO2 but not limited to CO2) passes. The gas introduced through the generator can be further cooled by passing the gas through an externally connected auxiliary heat exchanger maintained between -110 °C and +4 °C before being introduced into the metal / glass container. Between the generator and the wafer holder, an anodic aluminum oxide membrane (AAO) is placed. The nanopores in the AAO membrane help to form and can form nanobubbles, and then due to the lower density of the nanobubbles compared to the surrounding processing liquid, the nanobubbles will move towards the irradiated wafer. The distance / height between the generator, the AAO membrane, and the wafer holder can be adjusted according to the required parameters. In addition, due to the principle of buoyancy, the nanobubbles can also play a role in locally supporting the sulfur wafer subjected to photon / electron and / or heat treatment.

[0094] Working principle: The pre-expansion of pure chalcogenide and / or doped chalcogenide and / or any mixture of two or more chalcogenides (but not limited to this) supported by nanobubbles is carried out by simultaneously performing flash expansion and nanobubble-supported cooling to generate an internal cavity. In this method, the gas to be selected (such as CO2) is introduced via a generator into a container containing a process liquid maintained between -110 °C and +4 °C. Although the size range of the introduced bubbles depends on the pore size of the generator, the bubble size can be reduced by placing an AAO membrane directly above the generator. Due to the low density of the introduced bubbles and the large size of the bubbles limiting the transport of the bubbles through the AAO membrane, these bubbles accumulate below the cavity containing the AAO membrane. Then, the transport of the gas can only occur through the AAO membrane, which contains pores with nanometer sizes, resulting in the formation of nanobubbles with submicron sizes, more preferably with sizes less than 200 nm. These nanobubbles further move towards the sulfur wafer, which is exposed to a high-intensity photon flux (preferably 120 J / cm 2 above) from an FLA / UV / IPL laser, thereby causing pre-expansion of the chalcogenide wafer (preferably sulfur), and the nanobubbles not only assist / help in cooling and maintaining the structural integrity of the sulfur wafer, but also contribute to the generation of the internal cavity. The wavelength of the FLA / UV / IPL laser is maintained between the blue to UV range.

[0095] To induce ROP, high-energy photons with appropriate frequencies (such as the UV-C range from 200 nm to 280 nm and / or the VUV range from 100 nm to 200 nm) are used, and an ultrafast processing time (milliseconds) is sufficient. During this process, the incident photons from the FLA / UV / IPL device are absorbed by the sulfur wafer, resulting in local heating and ring-opening polymerization (ROP). Most of the photon energy delivered to the sulfur wafer is used for flash heating and subsequent expansion to reach a state with a density of approximately 1.66 g cm -3 . The surrounding process liquid immediately quenches the molten sulfur / polymerized sulfur and helps to inhibit the structure of the wafer. During the flash expansion process, the temperature of the process liquid is maintained between -110 °C and +4 °C with the help of a heat exchanger to avoid overheating, structural collapse, and vaporization of sulfur. The process liquid is circulated with the help of an external pump.

[0096] All processes mentioned in this disclosure involve two steps, which are preferably carried out simultaneously: the photon-induced expansion of sulfur at about 360 °C; and quenching between -110 °C and +4 °C (the ideal temperature being +4 °C). For this purpose, an energy source with minimal thermal inertia (such as FLA / UV / IPL) is preferably used as the heating source, and quenching is preferably carried out immediately to achieve the desired structural stability / transformation without the risk of vaporization. Commercial FLA equipment can operate at a heating rate of up to 100,000 °C per second, which causes sulfur to melt and collapse due to its low viscosity (similar to glycerol at 120 mPa at 60 °C). Sulfur wafers are prone to melting and collapsing when fusing / sealing all their internal cavities, which represents a complete failure. To prevent this, a structural support in the form of a graphene layer is provided and bonded / crosslinked to the sulfur and the process liquid used to fill the internal spaces / voids of the sulfur wafers. During this process, the liquid / vapor and gas expand simultaneously within the porous voids of the sulfur wafers. The processing liquid is converted into vapor and expands together with the vapor and gas inside the voids, thus counteracting the expansion caused by the photon-induced heating of the sulfur wafers. This instantaneous reaction prevents the structural collapse of the sulfur voids. The thin conductive layer coated on the sulfur wafers includes 2D materials (such as carbon), graphene / graphene oxide, and / or their derivatives (but not limited to this), and this thin conductive layer immediately reacts / crosslinks with the molten sulfur / polymerized sulfur. Sulfur radicals have unpaired electrons at both ends of the chain, and they react violently with graphene oxide (GO), reducing graphene oxide to r-GO (also known as deoxygenated GO), and forming a crosslinked / covalent / chemical bond-protective layer on the surface of graphene oxide, called "fish scales". This layer structurally strengthens the sulfur wafers during / after pre-expansion and ensures excellent electronic and ionic conductivity.

[0097] As summarized in Table 1, the pre-expansion of sulfur represents the state-of-the-art method for releasing the volume potential of sulfur. The first row represents a unitary body or monolithic 3D object formed by ordered nanocrystals of 1D / 2D monoclinic sulfur allotropes, and these nanocrystals together form a polycrystalline sulfur wafer, a quasicrystalline sulfur wafer, or a glassy crystalline sulfur wafer with hierarchical porosity. The main difference between the unitary wafers presented herein and the state-of-the-art slurry-based sulfur cathodes with a suitable 3D host (such as a graphene scaffold) lies in the presence of a particle-aggregate-cluster (PAC) network, which is common in both traditional lithium-ion batteries and the latest generation of post-lithium batteries.

[0098] Table 1. Volume expansion of different cathode materials.

[0099]

[0100] The coated electrode / cathode including expanded sulfur thus fabricated has a unique combination of internal (enclosed, inaccessible) and external (open, accessible) pores, which can also be occupied by the electrolyte or more preferably the catholyte. The pre-expanded sulfur cathode has better electrical conductivity, higher active material utilization, an E / S ratio of less than 1.5 ml / g, and the ability to internally buffer volume fluctuations during cycling without providing or generating additional open volume / pores. The pre-expanded pure chalcogenide and / or doped chalcogenide or any mixture of two or more thereof (preferably sulfur-based electrodes) can be used in electrochemical energy storage devices, i.e., secondary rechargeable batteries containing Li, Na, K, Ca, Mg, Al metals / ions as counter electrodes, or more specifically, high-energy Li-S batteries, Na-S batteries, Al-S batteries, Mg-S batteries, etc.

Claims

1. A method for expanding a chalcogenide material, the method comprising the following steps a to e: a) providing a free-standing porous chalcogenide material wafer; b) coating at least one layer of graphene oxide on the chalcogenide wafer; c) immersing the coated chalcogenide wafer into a process liquid; d) subjecting the immersed coated chalcogenide material to photon and / or electron irradiation, thereby increasing the temperature of the chalcogenide material to a range of 320° C. to 420° C., more preferably, subjecting the immersed coated chalcogenide material to photon and / or electron irradiation, thereby increasing the temperature of the chalcogenide material to 365° C., thereby expanding the chalcogenide material; e) placing the expanded chalcogenide material at a temperature lower than the T g The quenching is carried out at a glass transition temperature in the range of -196°C to 4°C. Preferably, the expanded chalcogenide material is heated at a temperature below the T of the chalcogenide. g Quenched at a glass transition temperature below -35°C, where The quenching medium is the process liquid and / or gas.

2. An electrode, for example, a cathode, comprising a chalcogenide material: a) wherein the chalcogenide material has expanded to a state in which the chalcogenide material exhibits a density state that is the same as a density state of a corresponding metal chalcogenide of the chalcogenide material; b) Among them, The apparent density of the chalcogenide material after expansion is within the range of the actual density of the corresponding metal chalcogenide and the chalcogenide itself; c) wherein the internal cavity of the chalcogenide material represents a buffer volume that can be used for volume compensation during battery charge / discharge; d) wherein the manufacturing process is characterized by a synergistic co-expansion of said chalcogenide material together with a process liquid and / or gas.

3. The electrode according to claim 2, wherein A 2D material is used to cover the surface of the chalcogenide material, and / or a 2D material is used to coat the surface of the chalcogenide material, and / or a 2D material is used to stabilize the surface of the chalcogenide material, wherein the 2D material is cross-linked with the chalcogenide material during the expansion process, and preferably, the 2D material is a graphene-based material, for example, the graphene-based material is graphene oxide.

4. The electrode according to claim 2 or 3, wherein The chalcogenide material is used as a redox active material, and wherein the mass content of the chalcogenide material is ≥85wt%, and the chalcogenide material exhibits multi-level porosity, wherein the open pores can be used for electrolyte / catholyte, and the closed pores are used as buffer volume that can be used for volume compensation.

5. An electrode according to any one of the preceding claims 2 to 4, wherein The chalcogenide material is selected from sulfur (S), selenium (Se) and tellurium (Te); in particular, the chalcogenide material is sulfur; further preferably, the chalcogenide material is a sulfur wafer.

6. An electrode according to any one of the preceding claims 2 to 5, wherein The characteristic volume compensation of the discharge products is distributed between open pores and closed pores, wherein the closed pores have the ability to compensate 0.25% to 100% of the total electrochemically driven theoretical volume expansion, corresponding to 79% from sulfur to Li2S, while the open pores compensate the remaining 0% to 50% of the total volume change of the discharged metal disulfide products.

7. The electrode according to claim 5, wherein The final product in the fully discharged state is Na2S and the volume compensation is partially covered by the following combination: ≤90% of the closed pores of the sulfur wafer that can be used and ≤45% of the open pores that can be used by the electrolyte, wherein the last 22% of the theoretical 157% conversion from sulfur to Na2S is not compensated, so that the volume fluctuation of the battery is limited to 22%.

8. The electrode according to claim 7, wherein the electrode is limited in an operating window, wherein: The final product of discharge is limited to Na2S2 and the theoretical 67% volume fluctuation of the final product of discharge is completely covered by the closed pores.

9. A laser-based apparatus for expanding and quenching a chalcogenide material to a state in which the chalcogenide material has a density comparable to that of a metal chalcogenide.

10. The laser-based device of claim 9, wherein: The wavelength of the photons is in the range of 430 nm to 100 nm, and more preferably, the wavelength of the photons is 390 nm.

11. A FLA / IPL-based apparatus for expanding and quenching a chalcogenide material to a state in which the chalcogenide material has a density comparable to that of a metal chalcogenide.

12. The FLA / IPL-based device according to claim 11, wherein: The wavelength of the photons is in the range of 800 nm to 170 nm, more preferably, the wavelength of the photons is in the range of 450 nm to 250 nm.

13. The FLA / IPL-based device according to claim 12, wherein: The FLA / IPL source generates 25 J / cm 2 or higher, preferably, the FLA / IPL source generates a high intensity photon flux of 120 J / cm 2 High intensity photon flux above the fluence.

14. The laser-based device of claim 9, wherein: The laser source generates a power of 100 J / cm 2 Up to 400J / cm 2 More preferably, the laser source generates a high intensity photon flux with a fluence in the range of 250 J / cm 2 High intensity photon flux above the fluence.

15. The laser-based device of claim 9, wherein: The laser beam is directed through the process liquid / quenching liquid. 16 . An electrode, in particular, a cathode, comprising the expanded chalcogenide material prepared by the method according to claim 1 .

17. A battery comprising the electrode according to claim 16, in particular, the electrode is a cathode.

18. The battery according to claim 17, wherein the ratio of electrolyte to sulfur (E / S) of the battery is less than 1.99 ml / g.

19. An apparatus for executing the method according to claim 1, the apparatus comprising: - a chamber for placing a wafer comprising a chalcogenide material, in particular, a chamber for placing a wafer comprising sulfur; a radiation source for photonically expanding the chalcogenide material, in particular for photonically expanding sulfur; and - A control system for regulating the expansion process.

20. The apparatus according to claim 19, further comprising: a movable arm carrying the radiation source, in particular a laser source, and comprising means for providing a flow of liquid towards the wafer; as well as - A holding device, which is used for the wafer, and has a rotation function. The holding device can rotate in a clockwise and / or counterclockwise direction at a desired speed. Preferably, the holding device can rotate in a clockwise and / or counterclockwise direction at a speed of 15 to 20 revolutions per minute.

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