Monolithic wafer-like cathodes grown synergistically from polycrystalline and amorphous glass-like domains and methods of making same

Abstract

Disclosed is a method for preparing a chalcogenide / sulfur cathode for an alkali metal secondary battery, in which sulfur and / or other chalcogenide and / or mixtures represent both the active material and a removable template / porogen, additionally defined as a glass / amorphous / polymer sulfur wafer, wherein the content of the active substance is defined by glassy sulfur and the porosity is determined by a crystalline phase template, having the following steps: growing a chalcogenide / sulfur wafer containing a tailored content of glass / polymeric and crystalline allotropes from a mother liquor via a suitable growth process, the chalcogenide / sulfur wafer has a specific presence / gradient / area distribution of crystalline allotropes and glassy / polymeric allotropes; and removing the chalcogenide / sulfur crystalline allotrope-template / porogen from the chalcogenide / sulfur glass-crystalline wafer by immersing the chalcogenide / sulfur glass-crystalline wafer in a suitable solvent; a defined porosity is created within the wafer by etching the crystalline phase from a glass-crystalline wafer-like cathode and leaving a 3D glassy / polymeric chalcogenide / sulfur, where in a further incubation stage, due to the metastability of the glass / polymer allotropes, the porosity of the 3D glassy / polymeric chalcogenide / sulfur is increased. A transition to gamma monoclinic sulfur, more preferably with trace amounts of glass / polymer allotropes, is produced, cross-linked with graphene-based and / or other suitable one or more comonomers and / or end-capping agents.

Description

[0001] According to the features of the independent patent claims, the present application relates to a method for producing a chalcogenide / sulfur cathode for an alkali metal secondary battery, a correspondingly produced cathode, and a secondary battery containing such a cathode.

[0002] The past decade has witnessed extensive research in both science and industry on high-capacity and high-energy-density rechargeable alkali metal ion and alkaline earth metal ion chalcogenide-based batteries, preferably lithium-sulfur (Li-S) batteries, as potential next-generation energy storage solutions.

[0003] Li-S battery technology promises unparalleled energy density for mobile electronics and electric vehicles. Due to the high specific capacitance of sulfur (1675 mAh g -1 ), high theoretical volume energy density (2800WL -1 ) and high gravimetric energy density (2600Whkg -1 ), as well as the large availability, low cost and environmental friendliness of sulfur as an active material, lithium-sulfur (Li-S) battery technology is one of the most promising next-generation energy storage solutions.

[0004] However, limited success has been achieved in the commercialization of Li-S batteries, primarily stemming from the loss of active materials during battery operation, termed lithium polysulfide shuttle (LPS), in which long chains of lithium polysulfides formed during the initial discharge of LiS batteries dissolve into the electrolyte and shuttle back and forth between the lithium metal anode and the sulfur cathode through the separator and ultimately redistribute on the cathode, causing pore blockage within conventional slurry-based cathodes and their reaction with the Li metal anode to form a resistive solid electrolyte interface (SEI), leading to rapid capacity decay and ultimately battery failure.

[0005] Exemplary efforts have been devoted to developing advanced cathodes and addressing LPS shuttling, but without much improvement in overall battery performance. Additionally, it is clearly not possible to achieve high gravimetric and volumetric energy densities using prior art slurry-based cathodes containing elemental / orthorhombic sulfur / carbon composites.

[0006] In traditional LiS batteries, the cathode is prepared via a classic slurry-based process that relies on the principle of particles, aggregates, and clusters (PACs). In such a concept, sulfur as the active material exists in confined spaces within the mesoporous / microporous carbon host, or chemically bonded to the host material such as GO, or as metal disulfides (Fe2S, Ag2S, etc.). Due to the presence of additional inactive materials such as the host, electronic carbon additives, and binders, this severely limits the presence of active materials within the cathode.

[0007] In addition, in this slurry-based cathode preparation method, the resulting porosity occupies a high volume percentage and is disordered and random, which leads to a high E / S ratio, i.e., the electrolyte-to-sulfur ratio is greater than 5 ml g -1 sulfur. As a result, the weight energy density and the volume energy density achievable from such Li-S batteries are significantly limited.

[0008] Document US10991944B2 discloses a monoclinic γ-sulfur phase within carbon nanofibers, which enables a Li-S battery to operate successfully for more than 4000 cycles in a carbonate electrolyte. This study discloses an altered redox mechanism for reversibly converting γ-sulfur to Li2S without forming long-chain soluble LPS during the charge / discharge process in a carbonate-based electrolyte. However, the synthesis of the stable γ-sulfur phase in this report involves a synthesis procedure of several hours, which is time-consuming and not scalable. In addition, a sulfur loading of less than 2 mg cm -2 and an E / S ratio of 20 are used, thus severely limiting the energy density achievable from such a cathode. Therefore, the application of such a cathode for high energy density applications is severely limited. However, this is a remarkable discovery and has the potential to overcome some of the classical challenges associated with the commercialization of Li-S batteries, mainly LPS shuttle mitigation.

[0009] Within a conventional slurry-based sulfur cathode, sulfur crystallizes in a thermodynamically stable room temperature allotropic phase, i.e., orthorhombic sulfur, also known as alpha sulfur (α-sulfur), with a density of 2.08 g cm -3 , which typically undergoes a two-step reduction reaction mechanism with commonly used ether-based organic electrolytes, also known as a solid-liquid-solid reaction. On the other hand, the use of carbonate electrolytes is not suitable due to the nucleophilic attack of LPS on carbonate substances (which leads to electrolyte consumption and the end of battery life). All other room temperature metastable sulfur allotropes tend to undergo a phase / structural transformation to the orthorhombic crystalline variant at room temperature. Via an aging process, the weight fraction of the polymeric / glassy / amorphous content relative to the crystalline content can be adjusted / customized.

[0010] By confining sulfur within a microporous / mesoporous porous host structure at a temperature above 155 °C (above which γ-sulfur is known to appear), it is possible to stabilize the monoclinic (γ), which is the densest form of sulfur (2.18 g cm -3 ). Once sulfur infiltrates the pores of this mesoporous-microporous host structure at high temperature, upon cooling, due to space constraints, i.e., orthorhombic α-sulfur requires a higher volume than monoclinic γ-sulfur, sulfur cannot undergo a phase transformation from monoclinic γ-sulfur to orthorhombic α-sulfur.

[0011] However, even if this monoclinic sulfur is stable within the host structure, it is still necessary to produce the cathode from this sulfur-permeated host via conventional slurry-based methods. In such slurry-based cathodes, the content of the active material (i.e., sulfur) is typically less than 67 wt% of the total cathode mass, thus significantly reducing the weight energy density. In addition, the porosity of such cathodes is typically about 45% of the total volume, which is disordered, thus limiting the 100% accessibility of the electrolyte to sulfur, thus reducing the sulfur utilization rate, and consuming a large amount of electrolyte to fill the porosity, thus again limiting the volumetric and weight energy densities.

[0012] An alternative solution for sulfur cathodes is based on copolymerized sulfur, such as a cathode based on sulfurized polyacrylonitrile (SPAN), which has shown thousands of stable cycles as a cathode in lithium-sulfur batteries. Although such cathodes limit the formation of long-chain polysulfide species that are soluble in common electrolytes, the total sulfur content within such copolymers is typically less than 60%, thus meaning a low amount of active material and thus a storage device with a low energy density.

[0013] To improve the performance of LiS batteries, namely high sulfur utilization rate, cycle life, and high energy density, not only a high sulfur loading within the cathode is required, but also the required porosity for volume compensation that occurs during charging / discharging, and the possibility of limiting the E / S ratio to less than 1.5 ml g -1 which can achieve high sulfur utilization rate as well as high weight and volumetric energy densities during battery operation.

[0014] What the applicant recently proposed and as described, for example, in document WO 2021233965 (the content of which is incorporated herein by reference) is a unique method for producing a self-supporting sulfur / chalcogenide positive electrode (cathode) based on direct crystal imprinting / injection to grow and stabilize rare monoclinic γ-sulfur for Li-S battery applications, which promises excellent performance.

[0015] The process of direct crystal imprinting / injection is also briefly disclosed in document EP 3913705 A1 (which is also incorporated herein by reference) as a method for producing a branched and / or hyperbranched monolithic sulfur structure cathode body (i.e., sulfur wafer), wherein aligned monoclinic sulfur crystals directly grow from a sulfur mother liquor maintained within a temperature range of 95 °C to 120 °C, where the monoclinic β-phase is known to be stable and grows in a needle-like morphology, and results in the formation of a sulfur crystal wafer having the desired hierarchical porosity induced by the density, population, and orientation of the seeds / nucleation centers within the grown monolithic sulfur wafer.

[0016] The disclosed method is capable of not only growing monoclinic β-sulfur in the form of a monolithic crystal wafer suitable for sulfur-based cathode fabrication, but also stabilizing the unique monoclinic γ-sulfur allotrope.

[0017] Furthermore, the proof of concept of the disclosed technology can be further generalized to the growth of wafer-like structures from other materials (e.g., Si, Ge, Sn, Ag and other metals or alloys, etc.), and represents a new branch of 3D printing that builds 3D objects with nanometer / micrometer scale resolution by controlled nucleation, followed by crystallization / solidification (in the case of crystalline / glassy / amorphous materials) and subsequent growth of macro-scale 3D wafer-like objects.

[0018] According to the direct crystal imprinting / implantation method, an aligned / hierarchically distributed seed carrier serves as a host / substrate with defect / host sites. The defect / host sites present on the surface of the seed carrier, preferably but not limited to single-walled carbon nanotubes with a diameter of 5 nm, serve as nucleation sites for growing nanocrystals, which subsequently form a 3D polycrystalline needle-like structure with a tailored and hierarchical porosity determined by the presence of the aligned seed carrier floating on the surface of the growth medium.

[0019] The seed crystals align on top of the mother solution via external stimulation (i.e., electrical and / or magnetic stimulation). These aligned single-walled carbon nanotubes further act as an artificial electron percolation and heat conduction network within the growing wafer, thereby reducing electron tortuosity and enabling high-speed operation of the resulting LiS battery containing a monolithic sulfur wafer.

[0020] The remaining problem with the direct crystal imprint / implantation method as described above is that it is only used to grow polycrystalline chalcogenide wafers with tailored porosity, which means that the porosity is part of the crystal wafer growth process, which makes it difficult to obtain well-grown wafers with matching porosity or to further tune the porosity.

[0021] It is therefore an object of the present invention to overcome the drawbacks mentioned above and to provide a grown sulphur wafer having the further possibility to adjust the porosity in an easy, economical, environmentally friendly and cost-effective manner.

[0022] This object is solved by a method, a cathode and a battery having the elements contained in the independent claims, while preferred embodiments of the invention are described by the elements of the dependent claims.

[0023] Generally provided according to the present invention is a monolithic self-supporting positive electrode (cathode) comprising a mixed glassy / amorphous / polymeric / crystalline allotrope of sulfur and / or a mixture of other chalcogenide glassy / amorphous / polymeric / crystalline allotropes, wherein the cathode is made by selective growth of a glassy / amorphous / polymeric / crystalline chalcogenide / sulfur wafer from a mother liquor, the wafer having a customized presence / gradient of crystalline and glassy / amorphous / polymeric allotropes, wherein during the process, the crystalline allotrope is removed / etched away by a suitable solvent. Thus, the crystalline sulfur and / or chalcogenide according to the present invention represents a pore former within the sulfur wafer to create the desired porosity in the sulfur / chalcogenide positive electrode (cathode).

[0024] According to the present invention, the presence and areal distribution of the crystalline allotrope acting as a pore former within the glassy / amorphous / polymeric allotrope defines the cathode porosity, wherein the distribution or pattern of the glassy / amorphous / polymeric allotrope is preferably inserted / transferred onto the surface of the mother liquor by a suitable method, preferably by laser-induced photon or electron radiation patterning or masking.

[0025] In the article “Laser-induced pattern formation in liquid sulfur - An indication of laser-induced phase transition to ordered polymer” by Y. Sakaguchi & K. Tamura, it is disclosed that irradiation of sulfur and / or other chalcogenides with photons and / or electrons results in ring-opening polymerization of sulfur and the possibility of drawing and / or injecting a predetermined pattern onto the surface of molten sulfur, thus further contributing to the regulation of the polymer content relative to the crystalline content within the molten sulfur.

[0026] From the perspective of solubility, the polymeric and crystalline phases of sulfur exhibit different behaviors, wherein it is known that crystalline sulfur dissolves in various solvents such as CS2, while polymeric sulfur shows no dissolution.

[0027] This insoluble sulfur, such as the commercially available material crystex TM is a well-known industrial product for the vulcanization industry.

[0028] Based on the solubility difference between polymeric / glassy / amorphous and crystalline sulfur, crystalline sulfur can be used as a pore former (i.e., a porosity generator dissolved in a suitable solvent), leaving behind the insoluble glassy / amorphous / polymeric allotrope of sulfur, which according to the present invention constitutes the sulfur wafer and will be further processed to be used as a cathode within a secondary battery.

[0029] What the present invention achieves is that the porosity of the wafer forming the cathode can be adjusted and introduced via the dissolution of the crystalline allotropes present in the as-grown sulfur wafer. The weight fraction of glassy / amorphous / polymeric sulfur relative to the crystalline allotropes of sulfur is adjusted by irradiating the mother liquor with photons of appropriate energy. The as-grown wafer is then subjected to an etching process using a suitable solvent, which results in the dissolution of one and / or more crystalline allotropes of sulfur, leaving glassy / amorphous / polymeric sulfur. Thus, the crystalline allotropes of sulfur act as pore formers within the resulting sulfur wafer.

[0030] The generation of porosity within the as-grown sulfur wafer as defined herein, i.e., via solvent etching / extraction of the crystalline domains, can be further combined with sulfur wafers grown by the DCi growth method, where porosity is inherently part of the growth process. This means that depending on the volume % of porosity within the DCi-grown sulfur wafer, further porosity can be generated via solvent etching of the glassy / crystalline phases present within the DCi-grown wafer.

[0031] The porosity of the as-grown sulfur wafer is preferably macroporosity, the main purpose of which is to reduce the tortuous path of charge carriers to enhance the rate performance, where the combined micro / mesoporosity generated via solvent etching of the crystalline phase is responsible for the increased surface area and redox reaction area.

[0032] More specifically, provided is a method for preparing a chalcogenide cathode for alkali metal and alkaline earth metal secondary batteries, which has the following steps: growing a chalcogenide wafer containing glassy / amorphous / polymeric and crystalline allotropes of chalcogenide / sulfur from a mother liquor via a suitable growth process, and removing the crystalline allotropes of the chalcogenide by dissolving in a suitable solvent, generating a metastable wafer with a defined porosity by leaving glassy / amorphous / polymeric chalcogenide with possible trace amounts of crystalline allotropes, and incubating the metastable wafer in an incubation chamber, preferably at 108 °C, to recrystallize the sulfur allotrope nuclei by transforming them into preferably monoclinic β and / or γ sulfur via seeding partially trapped within the glassy / amorphous / polymer shell.

[0033] Preferably, prior to removing the crystalline allotropes, an additional step of adjusting the weight fraction of glassy / amorphous / polymeric chalcogenide relative to the crystalline chalcogenide within the wafer to a specific value is provided, where more preferably, adjusting the glassy / amorphous / polymeric weight fraction includes irradiating the mother liquor with photons and / or electrons for a predetermined duration, intensity, power, and / or pattern.

[0034] According to another preferred embodiment of the present invention, the step of growing a chalcogenide wafer includes growing a branched and / or hyperbranched monolithic sulfur structure cathode body, i.e., a sulfur wafer, wherein acicular monoclinic β-sulfur crystals are directly grown from a sulfur-containing mother liquor at a temperature between 95°C and 120°C by introducing aligned seed / nucleation centers and then quenching the resulting monolithic monoclinic sulfur structure between -8°C and -210°C (preferably below the glass crystallization temperature of sulfur).

[0035] The method according to the present invention further includes an additional step of coating the as-prepared grown wafer with a 2D material (such as graphene oxide) as disclosed in EP23198077.2 to form a transparent transition layer that covalently binds to sulfur at the graphene oxide / sulfur interface, resulting in the formation of reduced graphene oxide (rGO), which also imparts significant electronic conductivity to the resulting sulfur wafer and enables electrochemical / redox activity, wherein the graphene oxide coating can be implemented by: dip coating, vacuum filtration, spraying, layer-by-layer, spin coating, bar coating, slot die coating, roll-to-roll printing, screen printing, flexographic printing, lithographic printing, inkjet printing, or film stretching / coating, vacuum filtration, spraying, layer-by-layer, spin coating, bar coating, slot die coating, roll-to-roll printing, screen printing, flexographic printing, lithographic printing, inkjet printing, or film stretching.

[0036] Subsequent crosslinking between graphene oxide and sulfur is achieved by providing high-energy radiation to the transparent graphene oxide layer coated on the chalcogenide / sulfur wafer and exposing it to high-energy photons and / or electron radiation, wherein graphene oxide reacts with sulfur at the graphene oxide / sulfur interface, and the higher-energy radiation causes ring opening of sulfur, resulting in the subsequent in-situ deoxygenation of graphene oxide to reduced graphene oxide and crosslinking with sulfur radicals.

[0037] Furthermore, in an additional step, the wafer can be covered with a second thin layer of a 2D material, which is more preferably electronically conductive and permeable to charge carriers in the electrolyte, such as MXene, graphene oxide, etc.

[0038] The second coating can be formed by electrophoretic deposition and / or reduction of the second 2D material.

[0039] In essence, what is disclosed herein is an advanced monolithic cathode, i.e., a cathode for an alkali metal ion and / or alkaline earth metal ion sulfur battery and a battery having the same, and more particularly relates to a lithium-sulfur secondary cathode for a battery, the cathode exhibiting a customized, layered, and / or ordered porosity, which is derived from the synergistic growth / etching / warming of the following sulfur allotropes: glassy, amorphous, polymeric, and / or crystalline sulfur allotropes with an ordered and / or disordered arrangement of sulfur crystalline phases (i.e., orthorhombic, monoclinic beta (β), and monoclinic gamma (γ)) representing the pore-forming agent of the cathode, or other crystalline allotropes with ring-shaped and / or tadpole structures / lattices on a suitable seed carrier, and an amorphous glassy polymeric sulfur allotrope representing a negative resist, which is formed within the crystalline domain and dissolves at least a portion of the sulfur crystal representing the pore-forming agent from the cathode to obtain an insoluble chalcogenide / sulfur cathode with a defined porosity.

[0040] The presence, gradient, and area distribution of the crystalline allotropes within the glassy / amorphous / polymeric sulfur allotropes define the cathode porosity, wherein the distribution / pattern is inserted / transferred onto the surface of the mother liquor by a suitable method, such as adjusting the content of the polymeric phase relative to the crystalline phase by laser-induced patterning or masking methods. The mother liquor is defined herein as a molten liquid containing crystalline / ring-shaped allotropes and dissolved allotropes, and most preferably is a molten glassy / crystalline allotrope containing sulfur and / or other chalcogenides. The mother liquor can also be any solvent in which sulfur is dissolved. The preferred solvent should be able to dissolve more than 20 wt% of sulfur (such as CS2), ionic liquids, or eutectic solvents (such as Dowtherm TM A), where the mother liquor can subsequently be used to regrow sulfur wafers, as mentioned in EP 3913705A1.

[0041] The mother liquor further contains additives such as triethanolamine, but is not limited to other additives that allow the preferential growth morphology (such as 2D or sheet-like growth / orientation) of the resulting grown crystals, where the amount of the additive is customized within the range of 0 to 5 wt%.

[0042] The result is a self-standing monolithic sulfur wafer cathode, which is composed of a mixture of glassy / amorphous / polymeric / crystalline allotropes of sulfur and / or other chalcogenide glassy / amorphous / polymeric / crystalline allotropes, and is particularly used as a cathode for an alkali metal ion sulfur battery, capable of providing ≥700 Wh kg -1 and more preferably ≥1000 Wh kg -1 of specific energy and a cycle life of >1000 cycles at a 3C rate.

[0043] The present invention is based on a prior direct crystal imprinting / injection method, with the main difference being the presence of a customized content of glass / amorphous / polymeric phase within polycrystalline sulfur, where the crystalline allotropes act as pore formers.

[0044] The present invention provides significant advantages regarding the fabrication of porous sulfur cathodes, which are fabricated by artificially introducing porosity by adjusting the weight fraction of glass / amorphous / polymeric chalcogenide / sulfur relative to the crystalline allotropes of sulfur via etching the crystalline allotropes from the grown sulfur wafers using a suitable solvent. By using photon / electron irradiation of the mother liquor, the fraction and presence of glass / amorphous / polymeric sulfur can be finely tuned by controlling the ring-opening polymerization of sulfur beyond the thermally induced ring-opening polymerization of sulfur. The resulting as-grown wafers have hierarchical porosity and reasonable flexibility, enabling subsequent processes to be carried out on the precursor wafers to use them as cathodes. Additionally, the mass loading of such cathodes exceeds the prior art.

[0045] Also provided is a secondary alkali metal battery comprising a wafer prepared according to the method as described above, wherein at 100% depth of discharge, the negative / positive retains residual or ≤3% of monoclinic γ sulfur allotrope crystals, the crystal planes of which then represent carrier / lattice matching for further epitaxial growth of monoclinic crystals during battery recharge.

[0046] Further features and advantages can be obtained from the following description of the drawings attached to the present application, shown as:

[0047] Figure 1 : Simplified schematic diagram of an apparatus for growing glass-crystalline wafers via a direct crystal imprinting method;

[0048] Figure 2 : Simplified top view of laser irradiation on a grown sulfur wafer;

[0049] Figure 3 : Magnified view of a wafer subjected to laser irradiation;

[0050] Figure 4 : Simple schematic diagram of an etching process;

[0051] Figure 5 : Possible different types of glass-crystalline wafer structures via the method described in the present invention.

[0052] Figure 6 : SEM micrograph showing a sulfur wafer that has been subjected to laser irradiation and acts as a negative resist, such that the irradiated areas are retained and the unirradiated areas are etched by the solvent.

[0053] Figure 7: A table showing the molecular composition of liquid sulfur at equilibrium after quenching the melt at various temperatures as described in 10.1007 / b12111.

[0054] Figure 8 : A schematic diagram of the ratio between vitreous sulfur and crystalline sulfur at various stages of the method according to the present invention.

[0055] Figure 1 A schematic diagram of the method according to the present invention is shown, in which in the first step, a Dci growth device is adapted to a glass / amorphous / polymeric / crystalline sulfur wafer, and the surface of the processing liquid 104 is laser-patterned with a laser 103 to create a customized presence of glass / amorphous / polymeric domains of sulfur relative to the crystalline domains in the growing wafer. 101 shows a simple mechanism for moving the wafer frame 102 that supports the growing wafer 105, which can be irradiated with a laser source for patterning. The processing liquid 104 is contained within a container 106. A top view of a simple arrangement of the device is also shown.

[0056] Figure 2 A simplified top view of laser irradiation on a growing sulfur wafer is shown, where the laser is used to adjust the weight fraction of polymeric / amorphous / vitreous sulfur relative to crystalline sulfur, thereby producing a glass-crystalline wafer 201.

[0057] Figure 3 is an enlarged view of a wafer that has been subjected to laser irradiation, showing the irradiated portion (A) and the non-irradiated portion (B). The irradiated portion consists mainly of polymeric / amorphous / vitreous sulfur, while the non-irradiated is crystalline sulfur that acts as a pore-forming agent during a subsequent etching process.

[0058] Once a glass / amorphous / polymeric / crystalline sulfur wafer has been grown, it is lifted from the surface of the mother liquor and immersed in a suitable solvent (here, for example, CS2 or an ionic liquid), and the crystalline phase that acts as a pore-forming agent in the as-grown wafer is etched away. Figure 4 is a simple schematic diagram of the etching process, in which the glass-crystalline wafer is subjected to treatment in a solvent / etchant 401 that can dissolve crystalline sulfur, resulting in the retention of polymeric sulfur and crystalline sulfur enclosed within polymeric / amorphous / vitreous sulfur that is inaccessible to the solvent / etchant.

[0059] In the next step, the glass / amorphous / polymeric sulfur wafer is coated with a 2D material (such as graphene oxide) and subjected to photon / electron irradiation, which results in the ring-opening polymerization of sulfur, the deoxygenation of graphene oxide to form reduced graphene oxide (rGO), and crosslinking between the two. The details of the crosslinking process of the photon / electron transparent 2D layer and its subsequent crosslinking are described in EP23198077.

[0060] The resulting graphene oxide-coated electrode (also referred to as a "herringbone coating") is subjected to incubation at a temperature of 108 °C, where the glassy / amorphous / polymeric sulfur will recrystallize again into the crystalline monoclinic β and / or γ phases. Due to the stability of the monoclinic β and / or γ phases at this temperature and the metastability of the glassy / amorphous / polymeric sulfur, this glassy / amorphous / polymeric-to-crystalline transformation is favorable. The incubation temperature plays a key role here because a direct transformation of the glassy / amorphous / polymeric sulfur into the crystalline monoclinic phase is desired. It is important to note that such a graphene oxide coating forms a shell, while the underlying sulfur forms a core. Once this step is completed, the glassy-crystalline sulfur and / or chalcogenide cathode is ready for / transferred to the subsequent cathode manufacturing process.

[0061] Figure 8 A schematic diagram showing the ratio between the glassy / amorphous / polymeric and crystalline sulfur at various stages and / or steps of the method 400A according to the present invention is shown. From Figure 8 it can be seen that within the conventionally thermally heated sulfur, at step 401, the maximum ratio between the glassy / amorphous / polymeric and crystalline sulfur can be observed at 243 °C, i.e., 40:60.

[0062] However, by using laser / electron beam patterning on the surface of the mother liquor, the ratio between the glassy / amorphous / polymeric and crystalline sulfur within the sulfur wafer can be adjusted, where the weight fraction of the glassy / amorphous / polymeric sulfur can be increased to a value of 65%. The ratio of the glassy / amorphous / crystalline domains is preferably maintained at 65:35 until the wafer growth is completed at 402 and the wafer is lifted / removed from the mother liquor at 403. The resulting sulfur wafer is immersed in a suitable etching solvent such as CS2 or a highly sulfur-soluble ionic liquid, where the crystalline sulfur is completely removed at 404.

[0063] After dissolving / etching the grown sulfur wafer in the etching solvent and removing the crystal allotropes / pore formers, the resulting cathode mainly contains glassy / amorphous / polymeric domains, such that the weight fraction of the crystalline sulfur preferably remains below 1 wt%, but is not limited thereto, and the porosity of the resulting wafer with only residual crystalline sulfur allotropes within the glassy / amorphous / polymeric allotropes is ≤ 35%.

[0064] During the subsequent process of coating with the 2D material at 405, the ratio between the glassy / amorphous / polymeric and crystalline sulfur remains unchanged, i.e., preferably but not limited to 99:1.

[0065] The resulting 2D material-coated sulfur wafers are then subjected to laser or flash lamp annealing to cause crosslinking of sulfur with graphene oxide and pre-expansion of sulfur at 406, after which the ratio of vitreous / amorphous / polymeric and crystalline sulfur is changed, more desirably but not limited to a change to 99.5:0.5. Thus, this means that the resulting wafers after such laser or flash treatment mainly contain vitreous / amorphous / polymeric sulfur and a porosity of ≤35 vol%. Herein, the 2D material, more preferably graphene oxide, forms a shell and the underlying sulfur forms a core, where graphene oxide crosslinks with sulfur at the graphene oxide / sulfur interface.

[0066] In a subsequent manufacturing step, at step 407, the fish-scale coated grown sulfur wafers are transferred to an incubation chamber and held at 108 °C for 30 minutes. At step 408, sulfur recrystallizes into monoclinic allotropes, more preferably β-sulfur and / or γ-sulfur, within the core of the sulfur wafers, such that the phase fractions between vitreous / amorphous / polymeric and crystalline sulfur are changed, such that the ratio can vary between 10:90, 8:92, 4:96 and more desirably to 5:95, which means that the resulting sulfur wafers now mainly consist of a crystalline sulfur allotrope core and a vitreous / amorphous / polymeric allotrope shell coated with graphene oxide / reduced graphene oxide.

[0067] At the end of the sulfur wafer growth and manufacturing process at 409, the resulting glass / polymeric / amorphous / crystalline wafers mainly contain crystalline sulfur, where the ratio between vitreous / amorphous / polymeric and crystalline sulfur can vary between 10:90, 8:92 and more preferably 4:96, and the wafers are ready for subsequent cathode manufacturing process steps.

[0068] The obtained wafers can then be used in a pre-expansion process as described in patent EP23219761.6. The glass-crystalline wafers are transferred to an ultra-fast pre-expansion device, where the temperature of the device can vary between -110 °C and +4 °C. Next, the glass / crystalline wafers are immersed in a treatment liquid at -110 °C to +4 °C, preferably below the glass transition temperature of sulfur, and exposed to a light source having >15 J / cm 2 at 500 nm. By means of intense pulsed light / flash annealing, the flash heat of the glass-crystalline wafers reaches a temperature of +365 °C / 5 ms. The excess treatment liquid absorbs heat from the photon pre-expanded wafers, which are quenched and subsequently have a temperature of -8 °C. Now the wafers with a preferred ratio of 99.5:0.5 of glass / crystalline domains are pre-expanded to 1.66 g / cm 3The density, which is equal to the density of Li2S, and thereafter the wafer with a glass / crystalline domain ratio of 98:2 is transferred to the incubation chamber due to the fact that the photon-induced swelling is not limited by the polymer-crystalline equilibrium known from thermally induced ring-opening polymerization, such that 98:2 represents a possible shielding loss of carbon nanotubes or other additives present in the cathode.

Claims

1. A method for preparing a chalcogenide / sulfur cathode with customized porosity for an alkali metal or alkaline earth metal secondary battery, comprising the following steps: a. Growing a chalcogenide / sulfur wafer from a mother liquor via a DCI growth process, the chalcogenide / sulfur wafer comprising glassy / amorphous / polymeric and crystalline allotropes, the wafer having a crystalline domain and a presence / gradient / area distribution of the glassy / amorphous / polymeric allotropes; b. By immersing the glassy / crystalline chalcogenide / sulfur wafer in a CS2 solvent, at least partially removing / etching the crystalline allotropes of chalcogenide / sulfur from the glassy / crystalline chalcogenide / sulfur wafer, producing a metastable wafer with a defined porosity, the metastable wafer having traces of crystalline allotropes trapped within the chains of the glassy / amorphous / polymeric chalcogenide / sulfur, and c. Incubating the metastable wafer in an incubation chamber to recrystallize the sulfur allotrope nuclei.

2. The method according to claim 1, further comprising the step of customizing the mass / volume content, area distribution, and gradient of the crystalline allotropes within the glassy / amorphous / polymeric chalcogenide / sulfur relative to the glassy-crystalline chalcogenide / sulfur, wherein the glassy / polymeric allotropes remain in the wafer and become active materials during the incubation step, and the crystalline allotropes are removable templates / pore-forming agents, and then maintaining the mass / volume content, area distribution, and gradient at specific values via a suitable conditioning / aging process, wherein customizing the weight fraction of the glassy / amorphous / polymeric chalcogenide / sulfur relative to the crystalline chalcogenide / sulfur phase includes irradiating the mother liquor with photons and / or electrons using a suitable mask and / or pattern in the case of laser / electron beam.

3. The method according to claim 2, wherein irradiating the mother liquor with photons and / or electrons during the growth process of the glassy / amorphous / polymeric / crystalline wafer-like electrode includes laser-induced patterning and / or electron beam patterning.

4. The method according to any one of the preceding claims, wherein the process of growing the chalcogenide / sulfur wafer comprising glassy / amorphous / polymeric and crystalline allotropes from the mother liquor is a direct crystal injection process (DCi).

5. The method according to any one of the preceding claims, further comprising the step of stabilizing the wafer with a capping agent / crosslinking agent.

6. The method according to any one of the preceding claims, further comprising the step of subjecting the grown wafer to photon / electron-induced pre-swelling to remove / compensate for its swelling with a suitable charge carrier such as an alkali metal and / or alkaline earth metal ion during electrochemical cycling.

7. The method according to any one of the preceding claims, wherein the incubation / aging in the incubation chamber is carried out between the glass transition temperatures of the chalcogenide, more preferably up to 112 °C for sulfur.

8. The method according to any one of the preceding claims, wherein the step of growing the chalcogenide / sulfur wafer comprises growing a branched and / or hyperbranched single-piece chalcogenide / sulfur-structured cathode body, i.e., the chalcogenide / sulfur wafer, wherein aligned monoclinic chalcogenide / sulfur crystals grow in synergy with the glass / polymeric allotrope, and wherein the crystallized allotrope grows directly on the mother liquor from floating seeds aligned by dielectrophoresis, and the glass / polymeric allotrope grows between the crystallized phases present in the chalcogenide / sulfur-containing mother liquor at a temperature between 95 °C and 120 °C, and subsequently quenching the resulting single-piece monoclinic chalcogenide / sulfur structure between -8 °C and -210 °C.

9. The method according to claim 8, wherein the step of growing the chalcogenide / sulfur wafer comprises heating the mother liquor in a temperature range of 200 °C to 380 °C, more preferably 243 °C, wherein the insertion of the desired pattern is carried out within this temperature range; varying the weight fraction / ratio between different allotropes of the chalcogenide, more preferably sulfur; and subsequently quenching to a temperature below the glass transition temperature of the chalcogenide, more preferably sulfur.

10. The method according to any one of claims 8 or 9, wherein the solvent / etchant and / or quenching agent for quenching the glass / amorphous / polymeric / crystalline allotrope and removing / etching the crystalline allotrope from the resulting grown wafer is carbon disulfide (CS2), Dowtherm TM or a urethane-based ionic liquid, but limited to all suitable chalcogenide solvents / etchants maintained / transported within a temperature range such as between the solidus and liquidus temperatures of the solvent / etchant.

11. The method according to the preceding claim, wherein the grown wafer is covered with a layer of graphene oxide, preferably by electrostatically driven self-assembly, dip coating and / or spraying, and wherein after application, the graphene oxide layer is converted into a reduced graphene oxide transition interface layer covalently bonded to the sulfur wafer.

12. The method according to claim 11, wherein the step of covering the wafer with the transition layer comprises providing high-energy radiation to the transparent graphene oxide layer coated on the chalcogenide / sulfur wafer and exposing it to photons / electrons radiation of suitable energy, wherein the graphene oxide reacts with the glass / amorphous / polymeric sulfur of the wafer during irradiation, and results in the ring-opening polymerization of sulfur and the in-situ deoxygenation / partial reduction of graphene oxide to reduced graphene oxide.

13. The method according to claim 11 or 12, wherein the wafer is covered by a second layer of 2D material, the 2D material is formed by electrophoretic deposition and reduced graphene oxide, and the graphene oxide is modified or surface charged with a suitable metal cation such as but not limited to Fe 3+ to stabilize the wafer, and then Fe 3+ is reduced to Fe 0 to become a component of the coating layer.

14. The method according to claim 13, wherein the 2D material is a graphene oxide / metal composite.

15. A chalcogenide-based wafer cathode prepared according to any one of claims 1 to 14, which exhibits hierarchical porosity and tailored porosity, wherein a. the hierarchical porosity is the porosity resulting from the wafer growth process, b. the tailored porosity is the result of a post-treatment for extracting / etching the chalcogenide.

16. The cathode according to claim 15, wherein the distribution of the hierarchical porosity accounts for 50 - 100% of the total porosity volume, and the induced / tailored porosity accounts for 0 to 50% of the total porosity.

17. The cathode according to claim 15 or 16, wherein the tailored porosity is introduced by selectively etching / dissolving the crystalline allotrope of the chalcogenide, more preferably sulfur, from a mixture of glass / amorphous / polymeric / crystalline chalcogenide allotropes.

18. The cathode according to any one of claims 15 to 17, wherein the preferred distribution of the hierarchical porosity is 70% of the total porosity volume, and the customized porosity is the remaining 30% of the total porosity volume.

19. A cathode for an alkali metal battery, comprising at least one wafer prepared according to any one of claims 1 to 14.

20. A secondary alkali metal battery, comprising the cathode according to any one of claims 15 to 19.

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