Monolithic wafer-like cathode synergically grown from poly-crystalline and amorphous glass-like domain and method of producing thereof

Abstract

To provide a method for preparing a chalcogenide / sulfur cathode for an alkali metal secondary battery.SOLUTION: A method for preparing a chalcogenide / sulfur cathode for an alkali metal secondary battery, where sulfur and / or other chalcogenide and / or mixtures represents both active mass and removable template / porogen, or is defined as a glass / amorphous / polymeric sulfur wafer where the content of active mass is defined by the glassy sulfur and porosity is dictated by the crystalline phase template, with the steps of growing a chalcogenide / sulfur wafer, comprising tailored content of glass / polymeric and crystalline allotropes, having a specific presence / gradients / areal distribution of crystalline to glassy / polymeric allotropes from a mother liquid via a suitable growth process, and removing the crystalline allotropes-template / porogen of chalcogenide / sulfur from the chalcogenide / sulfur glass-crystalline wafer by immersion in a solvent, creating a defined porosity within the wafer by etching crystalline phase out from glass-crystalline wafer-like cathode and leaving 3D glassy / polymeric chalcogenide / sulfur.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present application is directed to a method for preparing a chalcogenide / sulfur cathode for an alkali metal secondary battery, to the cathode prepared thereby, and to a secondary battery containing it, according to the features of the independent patent claims. [Background technology]

[0002] The past decade has seen high-capacity, high-energy density rechargeable alkali-ion and alkaline-earth-ion chalcogenide-based batteries, preferentially lithium-sulfur (Li-S) batteries, being extensively investigated in both scientific and industrial circles as promising next-generation energy storage solutions.

[0003] Lithium-sulfur (Li-S) battery technology promises unparalleled energy density applicable to mobile electronic devices and electric vehicles. Lithium-sulfur (Li-S) battery technology offers the high specific capacitance (1675 mAh g) of sulfur. -1 ), high theoretical volumetric energy density (2800W L -1 ) and high mass energy density (2600Wh kg -1 ), sulfur as an active material is one of the most promising next-generation energy storage solutions due to its wide availability, low cost, and environmental friendliness.

[0004] However, the commercialization of Li-S batteries has met with limited success, primarily due to the loss of active material during battery operation known as the lithium polysulfide shuttle (LPS), in which long-chain lithium polysulfides formed during the initial discharge of a LiS battery dissolve in the electrolyte, shuttle across the separator between the lithium metal anode and sulfur cathode, and eventually redistribute onto the cathode, causing plugging of pores in conventional slurry-based cathodes and their reaction with the Li metal anode to form a resistive solid electrolyte interface (SEI), resulting in rapid capacity fade and ultimately battery failure.

[0005] Although commendable efforts have been made to develop advanced cathodes and address LPS shuttling, overall cell performance has not improved significantly. Additionally, it is clearly not possible to reach both high gravimetric and high volumetric energy densities using state-of-the-art slurry-based cathodes made of elemental / orthorhombic sulfur / carbon composites.

[0006] In traditional LiS batteries, the cathode is prepared via a classical slurry-based process that relies on the particle, aggregate, and cluster (PAC) principle. Within this concept, sulfur as the active material exists either in closed spaces within a mesoporous / microporous carbon host, chemically bound to a host species such as GO, or as a metal disulfide (Fe2S, Ag2S, etc.). This severely limits the presence of active material in the cathode due to the presence of additional inactive materials such as the host, electronic carbon additives, and binders.

[0007] Additionally, within such slurry-based cathode preparation techniques, the resulting pores occupy a high volume percentage and are irregular and random, resulting in a high E / S ratio, i.e., an electrolyte to sulfur ratio of 5 ml per gram of sulfur (5 ml g -1 ) Thus, both the gravitational and volumetric energy densities achievable from such LiS batteries are significantly limited.

[0008] Document US10991944B2 discloses a monoclinic γ-sulfur phase in carbon nanofibers that can successfully operate Li-S batteries for over 4000 cycles in carbonate electrolytes. This work discloses an altered redox mechanism that reversibly converts γ-sulfur to LiS during the charge / discharge process in carbonate-based electrolytes without forming long-chain soluble LPS. However, the synthesis of the stable γ-sulfur phase in this report involves a synthetic procedure of several hours, which is time-consuming and not scalable. Furthermore, the synthesis of γ-sulfur phases of 2 mg cm -2A sulfur loading of less than 0.01 and an E / S ratio of 20 were used, severely limiting the energy density that can be obtained from such cathodes. This severely limits the applicability of such cathodes to high-energy density applications. Nevertheless, this is a significant discovery and holds the promise of overcoming some of the classic challenges associated with commercializing LiS batteries, primarily the LPS shuttle.

[0009] In conventional slurry-based sulfur cathodes, sulfur is present in its thermodynamically stable room-temperature allotropic phase, i.e., 2.08 g cm -3 It crystallizes into orthorhombic sulfur, also known as alpha sulfur (α sulfur), with a density of 0.01 MPa (0.01 MPa), which is typically subjected to a two-step reduction reaction mechanism, also known as a solid-liquid-solid reaction, with commonly used ether-based organic electrolytes. In contrast, the use of carbonate electrolytes is unsuitable because LPS nucleophilically attacks the carbonate species, resulting in the consumption of the electrolyte and the end of the battery's life. All other room-temperature metastable sulfur allotropes are prone to phase / structural transformations to orthorhombic crystal changes at room temperature. Through the aging process, the weight fraction of polymeric / glassy / amorphous content relative to the crystalline content can be adjusted / tailored.

[0010] It is the densest form of sulfur (2.18 g cm -3 Stabilization of monoclinic (γ) sulfur can be achieved by confining sulfur within a micro / mesoporous host structure at temperatures above 155 °C, where γ sulfur is known to form. When sulfur is infiltrated into the pores of such a meso-microporous host structure at high temperatures, upon cooling, sulfur cannot undergo a phase transformation from monoclinic γ sulfur to orthorhombic α sulfur due to spatial confinement, i.e., orthorhombic α sulfur requires a larger volume than monoclinic γ sulfur.

[0011] Even if such monoclinic sulfur is stabilized within the host structure, cathodes from such sulfur-infiltrated hosts still need to be fabricated via conventional slurry-based methods. The content of the active material, i.e., sulfur, in such slurry-based cathodes is typically less than 67 wt. % of the total cathode mass, thereby significantly reducing the gravimetric energy density. Furthermore, the pores in such cathodes are typically around 45% of the total volume, which are irregular, limiting 100% accessibility of the electrolyte to sulfur, thereby reducing sulfur utilization and consuming a significant amount of electrolyte to fill the pores, again limiting both the volumetric and gravimetric energy densities.

[0012] Alternative sulfur cathode solutions are based on copolymerized sulfur systems, such as sulfur-modified polyacrylonitrile (SPAN)-based cathodes, which have demonstrated thousands of stable cycles as cathodes in lithium-sulfur batteries. Although such cathodes limit the formation of long-chain polysulfide species that are soluble in commonly used electrolytes, the total sulfur content in such copolymers is typically below 60%, implying a small amount of active material and therefore a low energy density storage device.

[0013] For improved LiS battery performance, i.e., high energy density with high sulfur utilization and cycle life, an E / S ratio of 1.5 ml g was required, along with a high sulfur loading in the cathode as well as a desired porosity for volume compensation during charge / discharge. -1 There is also a need for the possibility to limit sulfur to less than 0.1 wt %, which can enable both high gravimetric and volumetric energy densities along with high sulfur utilization during cell operation.

[0014] The applicant has recently proposed a unique methodology for creating self-supporting sulfur / chalcogenide positive electrodes (cathodes) based on direct crystal imprinting / implanting to grow and stabilize rare monoclinic gamma sulfur for Li-S battery applications, as described, for example, in document WO2021233965, the contents of which are incorporated herein by reference, and which promises superior performance.

[0015] The process of direct crystalline imprinting / implanting is also briefly disclosed in document EP 3913705 A1 (also incorporated herein by reference) as a method for producing branched and / or hyperbranched monolithic sulfur structure cathode bodies, i.e., sulfur wafers, in which oriented monoclinic sulfur crystals are grown directly from a sulfur mother liquor maintained at a temperature range between 95°C and 120°C. At that temperature, the monoclinic β phase is known to be stable and grow in an acicular morphology, resulting in the formation of sulfur crystal wafers with a desired hierarchical porosity induced via the density, population, and orientation of seed crystals / nucleation centers within the growing monolithic sulfur wafer.

[0016] The methodology as disclosed is capable of growing monoclinic β-sulfur in the form of monolithic crystalline wafers suitable for the fabrication of sulfur-based cathodes, as well as stabilizing the unique monoclinic γ-sulfur allotrope.

[0017] Furthermore, the proof of concept of the technology as disclosed can be further generalized to grow wafer-like structures from other materials, such as Si, Ge, Sn, Ag, and other metals or alloys, opening up a new field of 3D printing to build 3D objects with nano / microscale resolution by controlled nucleation followed by crystallization / solidification (in the case of crystalline / glassy / amorphous materials) and subsequent growth of macroscale 3D wafer-like objects.

[0018] According to the direct crystal imprinting / implanting methodology, an oriented / hierarchically distributed seed crystal carrier serves as a host / substrate bearing defect / host sites. The defect / host sites present on the surface of the seed crystal carrier (i.e., preferentially, but not exclusively, single-walled carbon nanotubes with a diameter of 5 nm) serve as nucleation points for growing nanocrystals, which subsequently form a 3D polycrystalline needle-like structure with tailored hierarchical pores governed by the presence of the oriented seed crystal carrier floating on the surface of the growth medium. The seed crystals are oriented on top of the mother liquor by external stimuli (i.e., electrical and / or magnetic). These oriented single-walled carbon nanotubes further function as artificial electron percolation and heat conduction networks within the grown wafers, thereby reducing electron tortuosity and enabling high-speed operation of LiS batteries containing the resulting monolithic sulfur wafers. A remaining problem with the direct crystalline imprinting / implanting method as described above is that it can only be used to grow polycrystalline chalcogenide wafers with matched vacancies, which means that the vacancies are part of the crystalline wafer growth process, making it difficult to reach a fully grown wafer with matched vacancies or to further adjust the vacancies. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] US10991944B2 [Patent Document 2] WO2021233965 [Patent Document 3] EP3913705A1 [Patent Document 4] EP23198077.2 [Patent Document 5] EP23219761.6 [Non-patent literature]

[0020] [Non-Patent Document 1] "Laser-induced pattern formation in liquid sulfur - An indication of laser-induced phase transition to ordered polymer" by Y.Sakaguchi & K.Tamura [Non-patent document 2] 10.1007 / b12111 Summary of the Invention [Problem to be solved by the invention]

[0021] Therefore, the object of the present invention is to provide a grown sulfur wafer that overcomes the drawbacks as mentioned above and has the possibility to further tailor the vacancies in a facile, economical, environmentally friendly and cost-effective manner. [Means for solving the problem]

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

[0023] The present invention generally provides a monolithic, self-supporting positive electrode (cathode) comprised of a mixture of glassy / amorphous / polymeric / crystalline allotropes of sulfur and / or a mixture of glassy / amorphous / polymeric / crystalline allotropes of other chalcogenides, wherein the cathode is fabricated from selective growth of glassy / amorphous / polymeric / crystalline chalcogenide / sulfur wafers from a mother liquor, with a matched presence / gradient of crystalline and glassy / amorphous / polymeric allotropes, wherein the crystalline allotropes are removed / etched away by a suitable solvent during the process. Thus, the crystalline sulfur and / or chalcogenides according to the present invention represent porogens in the sulfur wafers to create the desired pores in the sulfur / chalcogenide positive electrode (cathode).

[0024] According to the present invention, the presence and area distribution of the crystalline allotrope acting as a porogen within the glass / amorphous / polymeric allotrope defines the pores of the cathode, wherein the distribution or pattern of the glass / 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 paper "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 irradiating sulfur and / or other chalcogenides with photons and / or electrons results in the ring-opening polymerization of sulfur, as well as the delineation and / or implantation of predetermined patterns on the surface of molten sulfur, which can further aid in the adjustment of polymer content relative to crystalline content within the molten sulfur.

[0026] From the standpoint of solubility, the polymeric and crystalline phases of sulfur behave differently, where crystalline sulfur is known to dissolve in various solvents such as CS2, while polymeric sulfur does not.

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

[0028] Based on the difference in solubility between polymeric / glassy / amorphous sulfur and crystalline sulfur, crystalline sulfur can be used as a porogen, i.e., a porosity generating agent that dissolves in a suitable solvent to leave behind an insoluble glassy / amorphous / polymeric allotrope of sulfur, which, according to the present invention, will be further processed to constitute sulfur wafers and be used as cathodes in secondary batteries.

[0029] The present invention achieves the ability to tailor and introduce porosity into the wafers forming the cathode through the dissolution of 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 tailored through irradiation of the mother liquor with photons of appropriate energy. The as-grown wafer is then subjected to an etching process using a suitable solvent, which dissolves the crystalline allotrope(s) of sulfur, leaving behind glassy / amorphous / polymeric sulfur. The crystalline allotropes of sulfur thus act as porogens in the resulting sulfur wafer.

[0030] The creation of vacancies in as-grown sulfur wafers as defined herein, i.e., via solvent etching / extraction of crystalline domains, can be further combined with sulfur wafers grown via the DCi growing method, where the vacancies are an intrinsic part of the growth process. This implies that, depending on the volume % of vacancies in the DCi grown sulfur wafer, additional vacancies can be created via solvent etching of the glass / crystalline phase present in the DCi grown wafer.

[0031] The pores in the as-grown sulfur wafer are preferably macropores, whose primary purpose is to reduce the tortuous path of charge carriers for enhanced capacity rating, where a combination of micro / mesopores created via solvent etching of the crystalline phase is responsible for increasing the surface area and redox reaction area.

[0032] More specifically, provided is a method for preparing chalcogenide cathodes for alkali metal and alkaline earth metal secondary batteries, comprising growing a chalcogenide wafer comprising glass / amorphous / polymeric and crystalline allotropes of chalcogenide / sulfur from a mother liquor via a suitable growth process; removing the crystalline allotropes of the chalcogenide via dissolution in a suitable solvent, leaving behind a glass / amorphous / polymeric chalcogenide that may have trace amounts of the crystalline allotrope, thereby producing a metastable wafer with predetermined pores; and incubating the metastable wafer in an incubation chamber, preferably at 108°C, to recrystallize the sulfur allotrope core by transforming it to the preferred monoclinic beta and / or gamma sulfur via monoclinic beta and / or gamma sulfur seed crystals partially entrapped within the glass / amorphous / polymeric shell.

[0033] Preferably, prior to removal of the crystalline allotrope, an additional step is provided of adjusting the weight fraction of glass / amorphous / polymeric chalcogenide to crystalline chalcogenide in the wafer to a specific value, wherein more preferably, adjusting the glass / amorphous / polymeric weight fraction comprises irradiating the mother liquid 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 comprises growing a branched and / or hyperbranched monolithic sulfur structure cathode body, i.e., a sulfur wafer, by directly growing acicular monoclinic β-sulfur crystals from a sulfur-containing mother liquor at a temperature between 95°C and 120°C via the introduction of oriented seed crystals / nucleation centers, and subsequently quenching the resulting monolithic monoclinic sulfur structure at a temperature between −8°C and −210°C, preferably below the glass crystallization temperature of sulfur.

[0035] The method according to the invention also comprises the additional step of coating the as-grown wafer prepared as described above with a 2D material such as graphene oxide as disclosed in EP 23198077.2 to form a transparent transition layer that covalently bonds to sulfur at the graphene oxide / sulfur interface, resulting in the formation of reduced graphene oxide (rGO) and also imparting significant electronic conductivity to the resulting sulfur wafer and enabling electrochemical / redox activity, wherein the graphene oxide coating can be carried out by dip coating, vacuum filtration, spray coating, layer-by-layer deposition, 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, spray coating, layer-by-layer deposition, spin coating, bar coating, slot-die coating, roll-to-roll printing, screen printing, flexographic printing, lithographic printing, inkjet printing, or film stretching.

[0036] Subsequent cross-linking of graphene oxide with sulfur is achieved by delivering high-energy radiation to a transparent graphene oxide layer coated on a chalcogenide / sulfur wafer and exposing it to high-energy photon and / or electron irradiation, where graphene oxide reacts with sulfur at the graphene oxide / sulfur interface, where the high-energy irradiation causes ring-opening of sulfur, subsequently deoxidizing graphene oxide in situ to reduced graphene oxide, leading to cross-linking with sulfur radicals.

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

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

[0039] In effect, disclosed herein are advanced monolithic positive electrodes, i.e., cathodes, for alkali-ion and / or alkaline earth-ion sulfur batteries, and batteries having the same; more particularly, lithium-sulfur secondary cathodes for batteries exhibiting tailored, hierarchical, and / or ordered porosity resulting from the synergistic growth / etching / incubation of glassy, ​​amorphous, polymeric, and / or crystalline sulfur allotropes with ordered and / or irregular arrangements of sulfur crystalline phases, i.e., orthorhombic, monoclinic beta (β), and monoclinic gamma (γ), or other crystalline allotropes with cyclic and / or tadpole-shaped structures / lattices, as cathode porogens, on a suitable seed crystal support, together with amorphous glassy polymeric sulfur allotropes as negative resists formed within the crystalline domains, and upon dissolution of at least a portion of the porogen sulfur crystals from the cathode, a non-dissolving chalcogenide / sulfur cathode with predetermined porosity is achieved.

[0040] The presence, gradient, and area distribution of the crystalline allotrope within the glassy / amorphous / polymeric sulfur allotrope defines the cathode pores, where 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. The mother liquor is defined herein as a molten liquid containing a crystalline / cyclic allotrope, a solubilized allotrope, with most preferred being a molten glassy / crystalline allotrope containing sulfur and / or other chalcogenides. The mother liquor can also be any solvent in which sulfur is dissolved. Preferred solvents should be capable of dissolving more than 20 wt.% sulfur, such as CS2, an ionic liquid, or a eutectic solvent such as Dowtherm™ A, where the mother liquor can subsequently be used to grow sulfur wafers, as also described in EP 3913705 A1.

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

[0042] The result is a free-standing monolithic sulfur wafer cathode consisting of a mixture of glass / amorphous / polymeric / crystalline allotropes of sulfur and / or a mixture of glass / amorphous / polymeric / crystalline allotropes of other chalcogenides, and in particular a specific energy of ≥ 700 Wh kg -1 , where more preferably ≥ 1000Wh kg -1 and can be used as a cathode for alkali-ion sulfur batteries, which can provide a cycle life of >1000 cycles at a 3C rate.

[0043] The present invention is based on previous direct crystalline imprinting / implantation methods, where the main difference is the presence of a glassy / amorphous / polymeric phase with an adapted content in polycrystalline sulfur, where the crystalline allotrope acts as a porogen.

[0044] The present invention offers considerable advantages for the fabrication of porous sulfur cathodes by utilizing artificially introduced vacancies through tuning the weight fraction of glass / amorphous / polymeric chalcogenide / sulfur relative to the crystalline allotrope of sulfur by etching the crystalline allotrope from the grown sulfur wafer using an appropriate solvent. By using photon / electron irradiation of the mother liquor to control the ring-opening polymerization of sulfur beyond thermally induced ring-opening polymerization, the fraction and presence of glass / amorphous / polymeric sulfur can be finely tuned. The resulting as-grown wafers possess reasonable flexibility with hierarchical vacancies, allowing for subsequent processing of precursor wafers for use as cathodes. Additionally, the mass loading of such cathodes exceeds the state of the art.

[0045] Also provided is a secondary alkali metal battery comprising a wafer prepared by the method as described above, wherein the anode / cathode ratio at 100% depth of discharge retains residual or ≦3% monoclinic gamma sulfur allotrope crystals, the facets of which then become supports / lattice matches for further epitaxial growth of monoclinic crystals upon recharging the battery.

[0046] Further features and advantages can be gleaned from the following description of the drawings attached to this application. [Brief explanation of the drawings]

[0047] [Figure 1] FIG. 1 is a simplified schematic diagram of an apparatus for growing glass crystal wafers via direct crystalline imprinting.

[0048] [Figure 2] FIG. 1 is a simplified top view of laser irradiation on an as-grown sulfur wafer.

[0049] [Figure 3] FIG. 1 is an enlarged view of a wafer being subjected to laser irradiation.

[0050] [Figure 4] FIG. 1 is a simplified schematic diagram of an etching process.

[0051] [Figure 5] 1A-1D illustrate different types of glass crystal wafer structures possible via the methods described within the scope of the present invention.

[0052] [Figure 6] 1 is an SEM micrograph showing a sulfur wafer that has been subjected to laser irradiation and acts as a negative resist, with the irradiated portions remaining and the unirradiated portions being solvent etched.

[0053] [Figure 7] 1 is a table showing the molecular composition of equilibrated liquid sulfur after quenching the melt at various temperatures as described in 10.1007 / b12111.

[0054] [Figure 8] 1 is a schematic representation of the ratio of glassy sulfur to crystalline sulfur at various stages of the method according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0055] Figure 1 shows a schematic representation of the method according to the invention, where in a first step, a Dci growth apparatus is adapted to a glass / amorphous / polymer / crystalline sulfur wafer, and the surface of a processing liquid 104 is laser patterned with a laser 103 to create glass / amorphous / polymer domains present that are adapted to the crystalline domains of sulfur in the growth wafer. 101 shows a simple mechanism for moving a wafer frame 102 that supports the grown wafer 105, which can be irradiated with a laser light source for patterning. The processing liquid 104 is contained in a vessel 106. A top view of this simple arrangement of the apparatus is also shown.

[0056] Figure 2 shows a simplified top view of laser irradiation on the grown sulfur wafer, where the laser is used to tailor the weight fraction of polymeric / amorphous / glassy sulfur to crystalline sulfur, thereby resulting in a glass crystal wafer 201.

[0057] Figure 3 shows a close-up of a wafer being subjected to laser irradiation, showing the irradiated (A) and unirradiated (B) regions. The irradiated region consists primarily of polymeric / amorphous / glassy sulfur, while the unirradiated region is crystalline sulfur, which acts as a porogen in the subsequent etching process.

[0058] Once the glass / amorphous / polymeric / crystalline sulfur wafer is 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, to etch away the crystalline phase that acts as a porogen in the as-grown wafer. Figure 4 shows a simplified schematic of the etching process, in which the glass-crystalline wafer is subjected to treatment with a solvent / etchant 401 capable of dissolving the crystalline sulfur, thereby preserving the polymeric sulfur and the crystalline sulfur encapsulated within the polymeric / amorphous / glassy 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 causes ring-opening polymerization of the sulfur and deoxygenation of the graphene oxide to form reduced graphene oxide (rGO) and crosslinks between them. Details of the crosslinking process of the photon / electron transparent 2D layer and subsequent crosslinking are described in EP23198077.

[0060] The resulting graphene oxide-coated electrode (also called "fish scale coating") is then incubated at 108°C, where the glassy / amorphous / polymeric sulfur recrystallizes into the crystalline monoclinic β and / or γ phases. This glassy / amorphous / polymeric-to-crystalline transformation is favored because the monoclinic β and / or γ phases are stable at this temperature, while the glassy / amorphous / polymeric sulfur is metastable. The incubation temperature plays a key role here, as a direct transition from the glassy / amorphous / polymeric sulfur to the crystalline monoclinic phase is desired. It is important to note that the graphene oxide coating forms a shell, while the underlying sulfur forms a core. Once this step is complete, the glassy-crystalline sulfur and / or chalcogenide cathode is ready for use / transfer to the subsequent cathode fabrication process.

[0061] 8 shows a schematic representation of the ratio between glassy / amorphous / polymeric sulfur and crystalline sulfur at various stages and / or steps of the method 400A according to the present invention. As can be seen from FIG. 8, in conventionally thermally heated sulfur, the maximum ratio of glassy / amorphous / polymeric sulfur to crystalline sulfur can be observed at 243° C., i.e., 40:60 in step 401.

[0062] However, by using laser / electron beam patterning of the mother liquor surface, the ratio between glassy / amorphous / polymeric sulfur and crystalline sulfur in the sulfur wafer can be tailored, where the weight fraction of glassy / amorphous / polymeric sulfur can be increased up to a value of 65%. The ratio of glassy / amorphous / crystalline domains preferably remains 65:35 until wafer growth is complete at 402 and the wafer is lifted / removed from the mother liquor at 403. The resulting sulfur wafer is subjected to immersion 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 dissolution / etching of the grown sulfur wafer in an etching solvent and removal of the crystalline allotropes / porogens, the resulting cathode comprises mainly glassy / amorphous / polymeric domains, with the weight fraction of crystalline sulfur preferably, but not limited to, remaining below 1 wt.%, resulting in a porosity of ≦35% for the resulting wafer with only crystalline sulfur allotropes remaining within the glassy / amorphous / polymeric allotropes.

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

[0065] The resulting sulfur wafer coated with the 2D material is then subjected to laser or flash light annealing at 406 to effect pre-expansion of the sulfur along with cross-linking of the sulfur and graphene oxide, after which the ratio of glassy / amorphous / polymeric sulfur to crystalline sulfur changes, more preferably, but not limited to, 99.5:0.5. Thus, the wafer obtained after such laser or flash treatment is primarily composed of glassy / amorphous / polymeric sulfur, implying a porosity of ≦35% by volume. Thus, the 2D material, more preferably graphene oxide, forms a shell, and the underlying sulfur forms a core, where the graphene oxide is cross-linked with sulfur at the graphene oxide / sulfur interface.

[0066] In a subsequent fabrication step, the fishscale-coated as-grown sulfur wafer is transferred to an incubation chamber and maintained at 108°C for 30 minutes in step 407. In step 408, recrystallization of sulfur into monoclinic allotrope, more preferably into β and / or γ sulfur within the core of the sulfur wafer, is carried out such that the phase fraction between glassy / amorphous / polymeric sulfur and crystalline sulfur is varied, with the ratio varying between 10:90, 8:92, 4:96, and more preferably 5:95, which implies that the resulting sulfur wafer now consists mainly of a core of crystalline sulfur allotrope and a glassy / amorphous / polymeric allotrope shell coated on graphene oxide / reduced graphene oxide.

[0067] At the end of the sulfur wafer growth and fabrication process at 409, the resulting glassy / polymeric / amorphous / crystalline wafer consists mostly of crystalline sulfur, where the ratio between glassy / amorphous / polymeric sulfur and crystalline sulfur can vary between 10:90, 8:92, more preferably 4:96, and the wafer is ready for the subsequent cathode fabrication process steps.

[0068] The resulting wafer can then be used in a pre-expansion process as described in patent EP23219761.6. The glass-crystal wafer is transferred to an ultrafast pre-expansion machine, where the temperature of the device can vary between -110°C and +4°C. The glass / crystal wafer is then immersed in a treatment solution between -110°C and +4°C, preferably below the glass transition temperature of sulfur, and is exposed to >15 J / cm2 at 500 nm. 2 The wafer is exposed to a light source of +365°C for 5 ms. Intense pulsed light / flash light annealing is used to flash heat the glass-crystal wafer to a temperature of +365°C for 5 ms. The excess processing liquid absorbs heat from the optically pre-expanded wafer, and the wafer is quenched and subsequently has a temperature of -8°C. The wafer, now with a preferred ratio of glass / crystal domains of 99.5:0.5, has a density of 1.66 g / cm, which is equal to the density of Li2S. 3The wafer is then pre-expanded to a density of 1000 Å, now with a glass / crystalline domain ratio of 98:2 (the 98:2 represents the potential for shielding losses of carbon nanotubes or other additives present inside the cathode, due to the fact that light-induced expansion is not limited by the polymer-crystalline equilibrium known from thermally induced ring-opening polymerization). The wafer is then transferred to an incubation chamber. [Explanation of symbols]

[0069] 101 Simple mechanism for moving wafer frames 102 Wafer Frame 103 Laser 104 Processing liquid 105 wafers 106 Container 201 Glass Crystal Wafer 401 Solvents / Etchants 400A Method according to the present invention

Claims

1. 1. A method for preparing a chalcogenide / sulfur cathode with tailored pores for an alkali metal or alkaline earth metal secondary battery, comprising: a. growing a chalcogenide / sulfur wafer comprising glass / amorphous / polymeric allotropes and crystalline allotropes, with a presence / gradient / area distribution of crystalline domains and glassy / amorphous / polymeric allotropes, from a mother liquor via a DCI growth process; b. at least partially removing / etching the crystalline allotrope of chalcogenide / sulfur from the glass / crystalline chalcogenide / sulfur wafer by immersing the wafer in a CS2 solvent to create a metastable wafer with predetermined vacancies having trace amounts of the crystalline allotrope trapped within the glass / amorphous / polymeric chalcogenide / sulfur chains; c. Incubating the metastable wafer in an incubation chamber to recrystallize the sulfur allotrope core. A method comprising:

2. 10. The method of claim 1, further comprising the step of matching the mass / volume content, area distribution, and gradient of the crystalline allotrope within the glassy / amorphous / polymeric chalcogenide / sulfur to the glass-crystalline chalcogenide / sulfur, The glass / polymer allotrope remains within the wafer and becomes an active mass during the incubation step. The crystalline allotrope is a removable template / porogen, which is then maintained at a specific value through an appropriate conditioning / aging process; A method wherein tailoring the weight fraction of glassy / amorphous / polymeric chalcogenide / sulfur to crystalline chalcogenide / sulfur phase comprises irradiating the mother liquor with photons and / or electrons using an appropriate mask and / or pattern in the case of laser / electron beam.

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

4. 10. The method of any one of the preceding claims, wherein the process for growing chalcogenide / sulfur wafers comprising glass / amorphous / polymeric allotropes and crystalline allotropes from a mother liquor is a direct crystalline implantation process (DCi).

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

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

7. 10. A method according to any one of the preceding claims, wherein the incubation / aging in the incubation chamber is carried out up to the glass transition temperature of the chalcogenide, more preferably up to 112°C in the case of sulfur.

8. The step of growing a chalcogenide / sulfur wafer includes growing a branched and / or hyperbranched monolithic chalcogenide / sulfur structure cathode body, i.e., a chalcogenide / sulfur wafer, wherein: Oriented monoclinic chalcogenide / sulfur crystals are grown synergistically with glass / polymer allotropes; growing the crystalline allotrope directly from a floating seed crystal oriented by dielectrophoresis on a mother liquor; The glass / polymer allotrope is grown between crystalline phases present in a chalcogenide / sulfur-containing mother liquor at temperatures between 95°C and 120°C.

10. A method according to any one of the preceding claims, wherein the resulting monolithic monoclinic chalcogenide / sulfur structure is subsequently quenched between -8°C and -210°C.

9. growing a chalcogenide / sulfur wafer; Varying the weight fraction / ratio between different allotropes of chalcogenides, more preferably sulfur, by heating the mother liquor between temperatures in the range of 200°C to 380°C, more preferably to 243°C, and effecting the desired pattern of intercalation within this temperature range; followed by quenching to a temperature below the glass transition temperature of the chalcogenide, more preferably sulfur; The method of claim 8, comprising:

10. The solvent / etchant and / or quenching agent used to quench the glass / amorphous / polymeric / crystalline and remove / etch the resulting crystalline allotrope from the grown wafer is carbon disulfide (CS). ２ 10. The method of claim 8 or 9, wherein the solvent is selected from the group consisting of: Dowtherm™, Dowtherm, or a carbamate-based ionic liquid, all of which are suitable as a chalcogenide solvent / etchant maintained / delivered within a temperature range between the solidus and liquidus temperatures of the solvent / etchant.

11. 10. The method according to the preceding claims, wherein the grown wafer is covered with a graphene oxide layer, preferably by electrostatically driven self-assembly, dipping and / or spray coating, and after application the graphene oxide layer is converted into a reduced graphene oxide transfer interface layer covalently bonded to the sulfur wafer.

12. 12. The method of claim 11, wherein the step of covering the wafer with a transfer layer comprises providing high energy radiation to a transparent graphene oxide layer coated on a chalcogenide / sulfur wafer and exposing it to photon / electron radiation of appropriate energy, wherein the graphene oxide reacts with the glass / amorphous / polymeric sulfur of the wafer during the irradiation process, resulting in ring-opening polymerization of the sulfur and in-situ deoxidization / partial reduction of the graphene oxide to reduced graphene oxide.

13. The wafer is covered with a second layer of 2D material by electrophoretically deposited and reduced graphene oxide, which may be modified or reduced with suitable metal cations, such as, but not limited to, Fe. ３＋ The surface is stabilized by providing a surface charge by Fe ３＋ Fe ０ 13. The method of claim 11 or 12, wherein the compound becomes an integral part of the coated layer by reduction to

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

15. 15. A chalcogenide-based wafer cathode prepared according to any one of claims 1 to 14 and exhibiting hierarchical and tailored pores, a. the hierarchical pores are pores derived from the wafer growth process; b. The tailored vacancies are the result of a post-treatment, which is chalcogenide extraction / etching; Chalcogenide wafer cathode.

16. The hierarchical pore distribution accounts for 50-100% of the total pore volume, and the induced / tailored pores account for 0-50% of the total pore volume.

16. The cathode of claim 15.

17. 17. The cathode of claim 15 or 16, wherein the tailored voids are introduced by selective etching / dissolution of the chalcogenide, more preferably the crystalline allotrope of sulfur, from a glass / amorphous / polymer / crystalline chalcogenide allotrope mixture.

18. 18. The cathode of claim 15, wherein the preferred distribution of hierarchical pores is 70% of the total pore volume, and the tailored pores are the remaining 30% of the total pore volume.

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

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

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