Hierarchical network cathode material for lithium-sulfur battery and preparation method thereof

Abstract

A lithium-sulfur cathode material, which may be incorporated into a lithium-sulfur battery, includes a sulfur host material configured to receive a sulfur electroactive material of circulating lithium ions. The sulfur host material comprises a fibrous carbonaceous network, an electroactive metal associated with the fibrous carbonaceous network, and a plurality of carbon nanotubes formed on the fibrous carbonaceous network. A method of making a lithium positive electrode material may include forming a porous membrane from aramid nanofibers, contacting a salt including an electroactive metal thereto, contacting a plurality of zeolitic imidazate skeleton-67 particles thereto, pyrolyzing to form a fibrous carbonaceous network having an electroactive metal, and removing the electroactive metal from the fibrous carbonaceous network. A plurality of carbon nanoparticles are then formed on a plurality of sites in the fibrous carbonaceous network.

Description

Cross-reference to related applications

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 452,867, filed March 17, 2023. The entire disclosure of the aforementioned application is incorporated herein by reference.

[0002] Government support This invention was completed with government support granted by the National Science Foundation (No. 1538180). The government holds certain rights to this invention. Technical Field

[0003] This disclosure relates to a cathode material for lithium-sulfur electrochemical batteries and a method for manufacturing such a cathode material, the cathode material comprising a graded sulfur host material configured to receive cyclic lithium ions as a sulfur electroactive material. Background Technology

[0004] This section provides background information relating to this disclosure, which is not necessarily prior art.

[0005] Lithium-sulfur (Li-S) electrochemical batteries or battery packs are known for their high energy density (2600 Wh / kg). -1 Large theoretical capacity (1675 mAhg) -1 Li-S batteries have become one of the most attractive energy storage platforms across various technological fields due to their cost-effectiveness and environmental friendliness. However, the practical application of Li-S batteries is still hindered by some thorny challenges, mainly stemming from the low conductivity of sulfur and its discharge products (Li2S2 / Li2S) and the presence of soluble lithium polysulfides (LiPS:Li2S). n The shuttle effect of 4≤n≤8) and the large volume expansion of the sulfur electrode during cycling lead to capacity loss.

[0006] Recent extensive research has focused on addressing these issues, including cathode structure optimization, multifunctional separators, novel electrolyte structures, and anode protection. For example, the design of the cathode or positive electrode in Li-S batteries has been a focal point. The molecular, nanoscale, and microscale morphology of the sulfur host in the cathode is crucial for efficient sulfur electrochemical reactions and improved battery performance. Various sulfur host materials, such as porous carbon, conductive polymers, graphene, carbon nanotubes, metal-organic frameworks, metal oxides / sulfides, and mixtures thereof, have been employed to attempt to improve the electrochemical performance of Li-S batteries. The design principle behind these studies is to impart accelerated lithium-ion (Li-S) reactions to the sulfur host. + Diffusion and electron transport enable easy sulfur electrochemical redox reactions and the desired sulfur fixation.

[0007] However, due to the relatively weak interaction between sulfur and lithium intercalation in nonpolar porous carbon, and the low conductivity of inorganic polar materials, there is still considerable room for improvement in the cycle life and overall performance of Li-S batteries, especially under long-cycle and high-sulfur loading conditions. Meanwhile, for most designs using sulfur-host materials derived from irregular particles or flakes, insufficient surface area and binding interaction sites limit the limited LiPS near the surface and are only effective for low-mass sulfur loading, severely compromising the energy density of the Li-S system and rendering these sulfur-host materials unsuitable for practical applications. Therefore, it is advantageous for sulfur-host materials to limit or minimize LiPS shuttle while providing efficient charge transport for high-load, non-conductive sulfur. Further breakthroughs are needed to meet the fundamental requirements of Li-S batteries, namely, combining sufficient sulfur loading, highly reversible specific capacity / areal capacity, high discharge rate capability, reduced lithium polysulfide shuttle, and operational durability. Summary of the Invention

[0008] This section provides a general summary of this disclosure, but does not fully disclose its entire scope or all its features.

[0009] In some respects, this disclosure relates to an electrode material for use in electrochemical cells.

[0010] In one aspect, the electrode material may include a fibrous carbonaceous network. A metal, such as an electroactive metal (e.g., a transition metal), may be associated with the fibrous carbonaceous network, and multiple carbon nanotubes may be disposed on the fibrous carbonaceous network.

[0011] In one respect, the plurality of carbon nanotubes may be nitrogen-doped.

[0012] In some respects, this disclosure also relates to a cathode material for lithium-sulfur electrochemical batteries.

[0013] In one aspect, the positive electrode may comprise a sulfur-host material configured to receive cyclic lithium ions as a sulfur electroactive material. The sulfur host may comprise a fibrous carbonaceous network. Cobalt (Co) may be associated with the fibrous carbonaceous network, and multiple carbon nanotubes may be disposed on the fibrous carbonaceous network.

[0014] In one respect, the plurality of carbon nanotubes may be nitrogen-doped.

[0015] In one aspect, the areal capacity of the positive electrode can be greater than or equal to about 17 mAhcm³. -2 .

[0016] In one aspect, the positive electrode may also comprise a sulfur-containing electroactive material. For example, the sulfur loading of the positive electrode may be greater than or equal to about 15 mg / cm³. 2 .

[0017] In some respects, this disclosure relates to a lithium-sulfur electrochemical battery.

[0018] In one aspect, the lithium-sulfur electrochemical battery may include a positive electrode. The positive electrode may include a sulfur-host material configured to receive recycled lithium ions as a sulfur electroactive material. The sulfur-host material may include a fibrous carbon network. Cobalt (Co) may be associated with the fibrous carbon network, and a plurality of carbon nanotubes may be disposed on the fibrous carbon network. The electrochemical battery may further include a negative electrode. The negative electrode may include lithium. The electrochemical battery may further include a separator disposed between the positive and negative electrodes. The electrochemical battery may further include an electrolyte that may be incorporated into at least one of the positive electrode, the negative electrode, and the separator. In one aspect, the areal capacity of the positive electrode can be greater than or equal to about 17 mAhcm³. -2 .

[0019] In one respect, the sulfur loading of the positive electrode can be greater than or equal to about 15 mg / cm³. 2 .

[0020] In one respect, the plurality of carbon nanotubes may be nitrogen-doped.

[0021] In one respect, the electrolyte-to-sulfur ratio (E / S) of the lithium-sulfur electrochemical battery may be less than or equal to about 8:1.

[0022] In some respects, this disclosure also relates to a method for manufacturing the positive electrode of a lithium-sulfur electrochemical battery.

[0023] In some aspects, methods for manufacturing electrodes for lithium-sulfur electrochemical batteries may include pyrolyzing a porous membrane formed from multiple aramid fibers or nanofibers and multiple metal-organic framework nanoparticles to form a fibrous carbonaceous network. The method may further include incorporating a transition metal into the fibrous carbonaceous network, and then forming multiple carbon nanotubes at multiple sites associated with the transition metal in the fibrous carbonaceous network to form a sulfur host material configured as a lithium-sulfur electroactive material for receiving recycled lithium ions.

[0024] In one aspect, the method further includes forming the porous membrane by spin-coating the plurality of aramid nanofibers and incorporating therein the plurality of metal-organic framework nanoparticles.

[0025] In one aspect, the metal-organic framework nanoparticles comprise a plurality of zeolite imidazole ester framework-67 (ZIF-67) particles, and the transition metal includes cobalt.

[0026] In one aspect, the method may include forming a porous membrane from aramid nanofibers, contacting a cobalt-containing salt with the porous membrane to incorporate cobalt therein, contacting a plurality of zeolite imidazole ester framework-67 (ZIF-67) particles with the porous membrane, and pyrolyzing the porous membrane to form a fibrous carbonaceous network having cobalt associated with the fibrous carbonaceous network. The method may also include forming a plurality of carbon nanoparticles at multiple sites (e.g., sites corresponding to the cobalt) in the fibrous carbonaceous network forming a sulfur host material configured as a sulfur electroactive material for receiving recycled lithium ions.

[0027] In some respects, this disclosure relates to an electrode material.

[0028] In one aspect, the electrode material may comprise a sulfur electroactive material and a sulfur host material configured to receive the sulfur electroactive material. The sulfur host material may comprise a fibrous carbonaceous network, an electroactive metal associated with the fibrous carbonaceous network, and a plurality of carbon nanotubes formed on the fibrous carbonaceous network.

[0029] In one aspect, the electroactive metal may include a transition metal.

[0030] In one aspect, the transition metal may include cobalt.

[0031] In one respect, the electroactive material can be adsorbed onto the surface of the fibrous carbon network.

[0032] In one respect, the electroactive material can be embedded in the fibrous carbon network.

[0033] In one aspect, the electroactive material can be adsorbed on the surface of the fibrous carbon network and embedded in the fibrous carbon network.

[0034] In one aspect, the plurality of carbon nanotubes may be formed at the sites of the electroactive metal on the fibrous carbon network.

[0035] In one respect, the plurality of carbon nanotubes may be nitrogen-doped.

[0036] In one aspect, the areal capacity of the electrode material can be greater than or equal to about 17 mAhcm³. -2 .

[0037] In one aspect, the sulfur loading of the electrode material can be greater than or equal to about 15 mg / cm³. 2 .

[0038] In some respects, this disclosure relates to a lithium-sulfur electrochemical battery.

[0039] On one hand, the lithium-sulfur electrochemical battery may include a positive electrode, a negative electrode, a separator disposed between the positive and negative electrodes, and an electrolyte incorporated into at least one of the positive electrode, the negative electrode, and the separator. The positive electrode may comprise a sulfur electroactive material and a sulfur host material configured to receive the sulfur electroactive material. The sulfur host material may comprise a fibrous carbonaceous network, an electroactive metal associated with the fibrous carbonaceous network, and a plurality of carbon nanotubes formed on the fibrous carbonaceous network. The negative electrode may comprise lithium.

[0040] In one aspect, the electroactive metal may include a transition metal.

[0041] In one aspect, the electroactive material can be adsorbed on the surface of the fibrous carbon network, the electroactive material can be embedded in the fibrous carbon network, or the electroactive material can be adsorbed on the surface of the fibrous carbon network and embedded in the fibrous carbon network.

[0042] In one aspect, the plurality of carbon nanotubes may be formed at the sites of the electroactive metal on the fibrous carbon network.

[0043] In one respect, the plurality of carbon nanotubes may be nitrogen-doped.

[0044] In one aspect, the areal capacity of the positive electrode can be greater than or equal to about 17 mAhcm³. -2 And the sulfur loading is greater than or equal to about 15 mg / cm³ 2 .

[0045] In one respect, the electrolyte-to-sulfur ratio (E / S) of the lithium-sulfur electrochemical battery may be less than or equal to about 8:1.

[0046] In some respects, this disclosure relates to a method for manufacturing electrodes for lithium-sulfur electrochemical cells.

[0047] In one aspect, the method may include contacting a salt containing an electroactive metal with a porous membrane, contacting an aerogel precursor with the porous membrane, pyrolyzing the porous membrane to form a fibrous carbon network having an electroactive metal associated with the fibrous carbon network, and forming a plurality of carbon nanoparticles at a plurality of sites in the fibrous carbon network, the fibrous carbon network forming a sulfur host material configured as a sulfur electroactive material to receive cyclic lithium ions.

[0048] In one aspect, the method may further include forming the porous membrane. The porous membrane may comprise aramid nanofibers.

[0049] In one aspect, the aerogel precursor may comprise a plurality of zeolite imidazole ester backbone-67 (ZIF-67) particles.

[0050] Further applications will become apparent from the description provided herein. The descriptions and specific examples in this summary are for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0051] The accompanying drawings described herein are for illustrative purposes only and not for all possible implementations, and are not intended to limit the scope of this disclosure.

[0052] Figure 1A -1G. Figure 1A The present invention schematically illustrates an example synthesis of a sulfur host material configured to receive a sulfur electroactive material, wherein the sulfur host material comprises a fibrous carbonaceous network formed of an aramid nanofiber (ANF) network having metal-organic framework nanoparticles (NPs), such as zeolite imidazolate frameworks (e.g., ZIF-67), which can self-assemble on the surface of the ANF, and an electroactive metal (e.g., cobalt) is associated with the fibrous carbonaceous network, thereby forming a plurality of carbon nanotubes on the fibrous carbonaceous network (NCZC) according to various aspects of the present disclosure. Figure 1B and Figure 1C These are scanning electron microscope images of ANF aerogel membranes at the 500 nm and 200 nm scales, respectively, prepared according to various aspects of the present invention. Figure 1D and Figure 1E These are ANF@ZIF-67 scanning electron microscope images at the 500 nm and 200 nm scales, respectively, according to various aspects of this disclosure. Figure 1F and Figure 1G These are scanning electron microscope images of NCZC at the 500 nm and 200 nm scales, respectively, according to various aspects of this disclosure.

[0053] Figure 2A – Figure 2H . Figure 2A – Figure 2E The images are transmission electron microscopy images of NCZC composites according to various aspects of this disclosure, showing the growth of multi-walled N-CNTs with highly graphitized walls, inner and outer diameters, cobalt, and lattice spacing. Figure 2A The scale is 500 nm. Figure 2B The scale is 200 nm. Figure 2C The scale is 20 nm. Figure 2D The size is 5 nm. Figure 2E The scale is 5 nm, and the circled areas are shown in more detail at the top right and bottom right. Figure 2F Carbon (C) is based on various aspects of this disclosure. 1s High-resolution X-ray photoelectron spectroscopy (see) Figure 2B ). Figure 2G Nitrogen (N) is based on various aspects of this disclosure. 1s High-resolution X-ray photoelectron spectroscopy (see) Figure 2C ). Figure 2H Cobalt (Co) is based on various aspects of this disclosure. 2p High-resolution X-ray photoelectron spectroscopy (see) Figure 2D ).

[0054] Figure 3A – Figure 3G . Figure 3A This illustrates a method according to various aspects of this disclosure, using a rate of 0.2C (1C = 1675 mAg). -1 ) and with 3.84 mg cm -2 The controlled sulfur loading is illustrated in the figure, showing the voltage curves of the NCZC electrode of the present invention compared with reduced graphene oxide (rGO) and Co-embedded porous carbon framework (CoCF) electrodes, where the x-axis represents capacitance and the y-axis represents voltage. Figure 3B This illustrates a method according to various aspects of this disclosure, using a rate of 0.2C (1C = 1675 mAg). -1 ) and with 3.84 mgcm -2 The controlled sulfur loading is used to compare the cycling performance of NCZC, rGO and CoCF electrodes in a graphical representation, where the x-axis represents the number of cycles, the y1-axis represents the capacity and the y2-axis represents the coulombic efficiency. Figure 3C This illustrates scan rates ranging from 0.2C to 10C (1C = 1675 mAg) according to various aspects of the invention. -1 A graphical representation of the rate performance of NCZC, rGO, and CoCF-based Li-S batteries, where the x-axis represents the number of cycles and the y-axis represents the capacity. Figure 3D This illustrates scan rates ranging from 0.2C to 10C (1C = 1675 mAg) according to various aspects of the invention. -1 The constant current charge-discharge curves of NCZC, rGO and CoCF-based Li-S batteries are graphically displayed, with the x-axis representing capacity and the y-axis representing voltage. Figure 3E This is a comparison of the electrochemical impedance spectra of NCZC, rGO, and CoCF electrodes according to various aspects of this disclosure. Figure 3F This is a graphical representation of the capacity decay of carbon-based electrodes derived from various metal-organic framework (MOF) nanoparticles per cycle. Figure 3G This is a graphical representation of the long-term cycling performance of the NCZC electrode at a rate of 1.0C for more than 2500 cycles according to various aspects of the present invention, where the a-axis represents the number of cycles, the y1-axis represents the capacity, and the y2-axis represents the coulombic efficiency.

[0055] Figure 4A – Figure 4E . Figure 4A This schematically illustrates Li2S according to various aspects of this disclosure. X Optimized configuration of (1≤x≤8) combined with C-Co-N NCZC sulfur host material. Figure 4B It shows Li2S X (1≤x≤8) Graphical representation of binding energy (Eb) on the NCZC electrode of the present invention, which consists of contrast rGO, contrast N-doped carbon, and C-Co-N prepared according to various aspects of the present invention. Figure 4C A graphical representation of the UV / Vis absorption spectra of Li2S4 solution before and after the addition of rGO and NCZC, with the inset showing optical photographs of Li2S4 captured by rGO and NCZC after 24 hours. Figure 4D and 4E According to various aspects of this disclosure, high-resolution XPS images of Li2S4 before and after adsorption are obtained. 2p and Li 1s The spectrum, where the x-axis represents binding energy and the y-axis represents intensity.

[0056] Figure 5A – Figure 5E . Figure 5A This is a graphical representation of the areal capacity of NCZC electrodes with different sulfur loadings prepared according to various aspects of this disclosure, where the x-axis represents the number of cycles and the y-axis represents the areal capacity. Figure 5B This illustrates the NCZC and representative high sulfur loadings (e.g., exceeding 5 mg / cm³) according to various aspects of this disclosure. -2 A graphical representation comparing the sulfur loading and areal capacity between electrodes, where the x-axis represents sulfur loading and the y-axis represents areal capacity. Figure 5C This demonstrates the NCZC electrode prepared according to various aspects of this disclosure at different rates from 0.2C to 5.0C and at 15.4 mg / cm². -2 A graphical representation of the rate performance under high sulfur loading, where the x-axis represents the number of cycles, the y1-axis represents capacity, and the y2-axis represents area capacity. Figure 5D This demonstrates the NCZC electrode according to various aspects of this disclosure at different rates from 0.2C to 5.0C and at 15.4 mg / cm². -2 The graph shows the constant current charge / discharge curves of a high sulfur load, where x1 axis represents capacity, x2 axis represents area capacity, and y axis represents voltage. Figure 5E This demonstrates the results at a 0.2 C ratio and 15.4 mg / cm² according to various aspects of this disclosure. -2The cycling stability and corresponding areal capacity of the sulfur-loaded NCZC electrode are graphically displayed, where the x-axis represents the number of cycles, the y1-axis represents the areal capacity, the y2-axis represents the capacity, and the y3-axis represents the coulombic efficiency.

[0057] Figure 6 This is a graphical representation of the charge / discharge curves of NCNC-based lithium-sulfur batteries prepared according to various aspects of this disclosure from the 1st to the 100th cycle, where the x-axis represents capacity and the y-axis represents voltage.

[0058] Figure 7A – Figure 7D . Figure 7A and Figure 7B The images are scanning electron microscope images at the 300 nm and 200 nm scales of ANF nanofibers calcined at 700 °C in an N2 atmosphere according to various aspects of this disclosure. Figure 7C and Figure 7D The images are transmission electron microscope images at the 100 nm and 10 nm scales of ANF nanofibers calcined at 700 °C in an N2 atmosphere according to various aspects of the present disclosure.

[0059] Figure 8 This schematically illustrates the relationship between lithium polysulfides (Li2S) according to certain aspects of the invention and comparative rGO. X Optimized configuration of NCZC HFN combined with pyridine N (1≤x≤8).

[0060] In different views, the corresponding reference numerals indicate the corresponding parts. Detailed Implementation

[0061] Providing example embodiments will make this disclosure thorough and will fully convey the scope to those skilled in the art. Numerous specific details (such as examples of specific components, parts, apparatus, and methods) are set forth to provide a thorough understanding of embodiments of this disclosure. It will be apparent to those skilled in the art that specific details are not required, example embodiments may be embodied in many different forms, and specific details should not be construed as limiting the scope of this disclosure. In some example embodiments, well-known processes, well-known equipment structures, and well-known techniques are not described in detail.

[0062] The terminology used herein is for the purpose of describing specific exemplary embodiments only and is not intended to be restrictive. As used herein, the singular forms “a,” “an,” and “the” may also be intended to include the plural forms unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having” are inclusive and therefore specify the presence of the stated features, elements, components, steps, integrals, operations, and / or parts, but do not exclude the presence or addition of one or more other features, elements, components, steps, integrals, operations, parts, and / or combinations thereof. While the open-ended term “comprising” should be understood as a non-restrictive term used to describe and claim the various embodiments described herein, in some respects it may also be understood as a more restrictive and binding term, such as “consisting of” or “substantially consisting of.” Therefore, for any given embodiment describing a composition, material, component, element, feature, integral, operation, and / or process step, this disclosure also specifically includes embodiments consisting of or substantially consisting of the said composition, material, component, element, feature, integral, operation, and / or process step. In the case of “consisting of…”, the alternative embodiments exclude any additional compositions, materials, components, elements, features, integers, operations and / or process steps. In the case of “consisting substantially of…”, any additional compositions, materials, components, elements, features, integers, operations and / or process steps that have a material effect on the basic and novel characteristics are excluded from the embodiments. However, any compositions, materials, components, elements, features, integers, operations and / or process steps that do not have a material effect on the basic and novel characteristics may be included in the embodiments.

[0063] Unless explicitly indicated as to the order of execution, any method steps, processes, and operations described herein should not be construed as requiring performance in the specific order discussed or illustrated. It should also be understood that additional or alternative steps may be employed unless otherwise stated.

[0064] When a component, element, or layer is referred to as “on another component, element, or layer,” “attached to another component, element, or layer,” “connected to another component, element, or layer,” or “coupled to another component, element, or layer,” the component, element, or layer may be directly on, directly attached to, connected to, or coupled to another component, element, or layer, or there may be intermediate components, elements, or layers. Conversely, when an element is referred to as “directly on another element or layer,” “directly attached to another element or layer,” “directly connected to another element or layer,” or “directly coupled to another element or layer,” there may be no intermediate elements or layers. Other terms used to describe relationships between elements should be interpreted in a similar manner (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0065] Although the terms first, second, third, etc., may be used herein to describe different elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms unless otherwise stated. These terms are used only to distinguish one step, element, component, region, layer, or part from another step, element, component, region, layer, or part. When used herein, terms such as “first,” “second,” and other numerical terms do not imply order or sequence unless the context clearly indicates otherwise. Therefore, without departing from the teachings of the example embodiments, the first step, first element, first component, first region, first layer, or first section discussed below may be referred to as the second step, second element, second component, second region, second layer, or second section.

[0066] For ease of description, spatial or temporal relative terms such as “before,” “after,” “inside,” “outside,” “below,” “below,” “under,” “above,” and “above” may be used in this document to describe the relationship between one element or feature and another element or feature, as shown in the figures. Spatial or temporal relative terms may be intended to cover different orientations of the device or system in use or operation other than those shown in the figures.

[0067] Throughout this disclosure, numerical values ​​represent approximate measurements or range limits to cover minute deviations from a given value and embodiments having approximately the stated value as well as embodiments having the precise stated value. Except for the working examples provided at the end of the detailed description, numerical values ​​of all parameters (e.g., quantities or conditions) in this specification (including the appended claims) should be understood to be modified in all cases by the term “about,” regardless of whether “about” actually appears before the numerical value. “About” indicates that the numerical value allows for some slight imprecision (numerically close to precision; approximately or reasonably close to the value; almost). If the imprecision provided by “about” cannot be otherwise understood in the art to have this common meaning, then “about” as used herein at least indicates a variation that may be caused by common methods of measuring and using these parameters. For example, “about” can include a variation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in some respects, optionally less than or equal to 0.1%.

[0068] In addition, the disclosure of a range includes disclosing all values ​​within the entire range and further subdivisions of the range, including endpoints and subranges given for the range.

[0069] The example implementation will now be described more fully with reference to the accompanying drawings.

[0070] High-energy-density electrochemical batteries, such as lithium-sulfur (LiS) batteries, can be used in a variety of applications. A typical lithium-sulfur battery includes at least one positive electrode or cathode, at least one negative electrode or anode, an electrolyte material, and a separator. Lithium-sulfur batteries operate by reversibly transferring lithium ions between the negative and positive electrodes. The positive electrode typically comprises a sulfur-host material containing a sulfur / sulfur compound that reversibly reacts with lithium, while the negative electrode can be lithium metal. A separator, such as a polymer separator, can be placed between the negative and positive electrodes. A liquid or solid electrolyte is also disposed between the positive and negative electrodes. For example, the liquid or solid electrolyte can be disposed within the pores of the separator. The electrolyte suitable for conducting lithium ions between the electrodes can be in solid and / or liquid form and / or mixtures thereof. For solid-state batteries that include solid electrodes and a solid electrolyte (or solid separator), the solid electrolyte (or solid separator) can physically separate the electrodes, thus eliminating the need for a distinct separator.

[0071] When the battery is charged, lithium ions move in a first direction between the cathode (positive electrode) and anode (negative electrode), while when the battery is discharged, lithium ions move in the opposite direction. Each negative and positive electrode is connected to a current collector. During battery use, the current collectors associated with the two electrodes are connected via an external circuit that allows current generated by electrons to flow between the electrodes to compensate for the transport of lithium ions.

[0072] Compared to semiconductor metal oxides, the low conductivity of sulfur and the small molecular size of lithium polysulfides pose fundamental challenges to lithium-sulfur batteries in terms of cycle life, discharge rate, and coulombic efficiency. Based on previous research on charge, mass, and stress transport in permeation networks, this disclosure addresses these challenges by providing a novel cathode material with a sulfur host material exhibiting a layered architecture.

[0073] In some aspects, a cathode material for lithium-sulfur electrochemical batteries is provided. The cathode or cathode may comprise a sulfur-host material configured as a sulfur-electroactive material to receive cyclic lithium ions. The layered sulfur host may comprise a fibrous carbonaceous network. The fibrous carbonaceous network can be formed by pyrolyzing an aerogel precursor produced from aramid polyamide or aramid nanofibers (referred to herein as PAF or ANF). In some variations, the aerogel precursor with ANF fibers may also have multiple metal-organic framework (MOF) particles, such as zeolite imidazole ester framework-67 (ZIF-67) particles, disposed on or mixed with the ANF fibers. Furthermore, the fibrous carbonaceous network also contains an associated cobalt (Co) metal, for example, which may be adsorbed on the surface of the fibrous carbonaceous network or embedded within it. Cobalt may be disposed on the surface of the fibrous carbonaceous network in the form of nanoparticles, for example, in one variant having an average diameter of about 20 nanometers. In some variations, reagents or conditions during the pyrolysis process can promote nitrogen (N) doping in carbon-based materials (generated by pyrolysis of aramid fibers).

[0074] Following the pyrolysis of the aerogel precursor, multiple carbon structures can be formed on a fibrous carbon network, for example, through deposition processes such as chemical vapor deposition (CVD) from multiple sites on the surface of the fibrous carbon network. In some respects, the carbon structures are carbon nanotubes formed on the fibrous carbon network, such as multiwalled carbon nanotubes (MWCNTs) or, alternatively, single-walled carbon nanotubes (SWCNTs). These sites may correspond to a portion of cobalt present on the surface and act as catalysts for the growth of nanotubes from it. In some variations, the carbon nanotubes are grown in an environment that promotes nitrogen (N) doping of the carbon nanotubes.

[0075] In this hierarchical sulfur host material, the high connectivity and conductivity of N-doped carbonized aramid nanofibers, which house cobalt (Co) nanoparticles (e.g., with an average diameter of less than about 20 nm) and N-doped carbon nanotubes (CNTs), create a multi-scale network that enables efficient charge transport, minimal dead volume, and strong binding of lithium polysulfides. More specifically, composite materials with multi-scale designed structures can be formed, comprising interconnected N-doped carbon nanofiber frameworks (NCNFs), cobalt-embedded porous carbon framework (CoCF) hybrids derived from aramid nanofibers (ANFs), and N-doped carbon nanotubes (N-CNTs) rooted in or connected to the CoCF. During synthesis, metal-organic framework nanoparticles (such as ZIF-67 nanoparticles) can be assembled onto a fibrous aerogel framework formed by aramid nanofibers (ANF) through electrostatic attraction and coordination. N-CNTs can then be grown via chemical vapor deposition (CVD) to further entangle the nanofibers and form a highly interconnected, self-supporting conductive framework (see [link to original text]). Figure 1A ).

[0076] Figure 1A The first step of a method for manufacturing the positive electrode of a lithium-sulfur electrochemical battery is shown, and will be described further below. Figure 1A At the top, a porous membrane is formed from aramid nanofibers, for example, by spin casting. This can be processed to form an aerogel porous membrane. Next, multiple zeolite imidazole ester framework-67 (ZIF-67) particles are contacted with or grown on the porous aerogel membrane. The precursor can then be pyrolyzed to form a fibrous carbonaceous network.

[0077] In some variations, self-supporting aramid nanofiber (ANF) films used as cathode substrates were prepared by spin coating (see [link to original text]). Figure 1B and Figure 1C Then, the ANF aerogel membrane was immersed in a methanol solution containing Co(NO3)2·6H2O, where Co... 2+ Ions adsorb onto the nanofibers and form coordination bonds with amide groups. Subsequently, nanoparticles (NPs) of the zeolite imidazole framework-67 (ZIF-67) can self-assemble on the surface of ANF (ZIF@ANF), as shown by scanning electron microscopy (SEM) (see [link]). Figure 1D and Figure 1EThe concentration of ZIF-67 on the ANF@ZIF precursor varied with immersion time (e.g., 1 hour, 2 hours, 3 hours, and 4 hours). With prolonged immersion time, cubic NPs also nucleated in solution and formed in the voids between nanofibers (ANF@ZIF-4).

[0078] A multi-scale network composite was obtained by catalytic CVD carbonization in a nitrogen (N2) atmosphere. In this process, ZIF@ANF can be pyrolyzed and transformed into a cobalt-containing / cobalt-intercalated porous carbon framework (CoCF) and an interconnected N-doped carbon nanofiber framework (NCNF) (CoCF@NCNF). In some aspects, N-doped carbon aerogel@Co-intercalated hierarchical carbon hybrid@CNT (denoted as HFN) composite electrode materials can be fabricated using chemical vapor deposition (CVD), a technique that may include thermal annealing of ANF@ZIF using melamine as a precursor without any additional catalyst. When melamine begins to decompose, NH3 and H2 are released. These gases facilitate the formation of active Co nanoparticles and promote the catalytic growth of N-CNTs on the surface from abundant carbon and nitrogen sources. CoCF acquires a morphology derived from the catalytic growth of N-CNTs (see [link to CVD]). Figure 1F and Figure 1G Unlike ANF-derived carbon nanofibers with smooth surfaces, the fibers in NCZC have rough surfaces and abundant bamboo-like N-CNT growth. The surface density of ZIF-67 NPs affects the morphology of the carbonized composite. For example, NCZC-4 exhibits lower uniformity than NCZC-3 due to its higher ZIF-67 NP content. In the absence of melamine, N-CNTs disappear after annealing.

[0079] Sulfur-host materials prepared by such processes and provided by various aspects of this disclosure possess a number of structural features that facilitate integration into a variety of transport requirements. For example, the highly three-dimensionally interconnected continuous carbon nanofiber network architecture provides uniform sulfur distribution, rapid electron conduction, and sufficient electrode / electrolyte interfaces for rapid ion transport. Furthermore, porous carbon units and N-CNT growth throughout the internal space of the fiber network provide more active sites for redox processes utilizing sulfur, which is particularly useful for high-sulfur-loaded systems. Additionally, the uniformly distributed nitrogen (N) and cobalt (Co) doped polar surfaces help confine lithium polysulfides (LiPS), contributing to minimizing or preventing LiPS shuttle. Moreover, the self-supporting electrode design has a large surface area, avoiding insulating polymer binders, thereby further enhancing electrode conductivity and accommodating volume changes of sulfur species during battery cycling.

[0080] In some respects, lithium-sulfur batteries incorporating such cathodes exhibit high rate capability up to 10C, with negligible capacity decay of 0.011% per cycle during ultralong cycling processes (e.g., over 2,500 charge / discharge cycles), and a capacity retention of up to approximately 15.4 mg cm⁻¹. -2 It has a capacity of 17.0 mAh / cm³ under high sulfur loading. -2 The high areal capacity and low electrolyte-to-sulfur ratio (E / S) of approximately 8:1 make batteries incorporating these cathodes ideal for many practical applications. These electrochemical parameters exceed those of leading commercial batteries using metal oxide cathodes by approximately 300% to approximately 500%, and exceed the DOE target of 300% for batteries used in electric vehicles.

[0081] In various aspects, this disclosure provides a lithium-sulfur electrochemical battery comprising a positive electrode containing a sulfur host material configured to receive cyclic lithium ions. The sulfur host material may comprise a fibrous carbonaceous network. Cobalt (Co), such as cobalt nanoparticles, may be associated with the fibrous carbonaceous network. Furthermore, the sulfur host material may comprise a plurality of carbon nanotubes formed on the fibrous carbonaceous network. The lithium-sulfur electrochemical battery may also include a lithium-containing negative electrode, a separator disposed between the positive and negative electrodes, and an electrolyte.

[0082] In one respect, the areal capacity of lithium-sulfur electrochemical batteries can be greater than or equal to approximately 17.0 mAh / cm³. -2 On the other hand, the sulfur loading of lithium-sulfur electrochemical batteries can be greater than or equal to approximately 15.3 mg / cm³. 2 On the other hand, the ratio of electrolyte to sulfur (E / S) in an electrochemical cell can be less than or equal to about 8:1.

[0083] The graph-based design of hierarchical networks based on nanofiber composites can also be extended to other materials for sustainable energy technologies that require high charge transport efficiency and mechanical strength.

[0084] It is further recognized that, in addition to lithium-sulfur batteries, porous hierarchical electrode materials can be used for other applications. These can include, in non-limiting examples, other energy storage such as supercapacitors, metal-ion or metal-air batteries, etc. In such applications, the electrode can comprise a porous material configured as an electroactive material to receive recycled lithium ions. The porous material can comprise a fibrous carbonaceous network and has one or more electroactive metals (e.g., transition metals such as cobalt (Co), manganese (Mn), nickel (Ni), aluminum (Al)) associated with the fibrous carbonaceous network. Further, the porous material has a plurality of carbon nanotubes formed on the fibrous carbonaceous network. The plurality of carbon nanotubes and / or the fibrous carbonaceous network can be doped with nitrogen (N).

[0085] The implementation of this disclosure is further illustrated by the following non-limiting examples.

[0086] Example 1 Preparation of ANF hydrogel membranes. Aramid nanofiber (ANF) dispersions were prepared according to J. Zhu et al., “Branchedaramid nanofibers.” Angew. Chemie Int. Ed. 56, 11744–11748 (2017), the relevant portions of which are incorporated herein by reference. In this example, 2 wt.% ANF dispersions were prepared in the presence of potassium hydroxide (KOH, Sigma-Aldrich) by using KEVLAR… TM A solution of dimethyl sulfoxide (DMSO, Sigma-Aldrich ≥ 99.9%) in 69 mL (from Thread Exchange) was stirred for one week until a deep red ANF solution was obtained. ANF hydrogel membranes were then prepared using a spin-coating method. Specifically, 2 mL of ANF (2 wt.%) dispersion was immersed in a clean glass slide and spin-coated at approximately 1500 rpm for about 30 seconds. Afterward, the glass slide was immersed in deionized water to remove DMSO and then stored in methanol (Sigma-Aldrich) solution for later use. It is important to note that before use, the glass slide should be cleaned in a piranha solution (3:1 H₂SO₄ / H₂O₂) for approximately 24 hours, followed by thorough rinsing with deionized water.

[0087] Example 2 Preparation of ANF@ZIF-67 composite aerogel membrane. To prepare the ANF@ZIF-67 composite membrane, an ANF membrane (4 cm x 4 cm) was first immersed in a 20.0 mM, 9 mL Co(NO3)2·6H2O (≥99.0%, Sigma-Aldrich) / methanol solution for approximately 10 minutes. Subsequently, approximately 160.0 mM, 15 mL 2-methylimidazole (99.0%, Sigma-Aldrich) / methanol was added to the above solution, and the mixture was magnetically stirred for approximately 10 minutes to allow for bonding. The ANF membrane was then stored in a purple solution at room temperature for different times (e.g., 1 hour, 2 hours, 3 hours, and 4 hours). The ANF@ZIF obtained at different reaction times (denoted as ANF@ZIF-1, ANF@ZIF-2, ANF@ZIF-3, and ANF@ZIF-4, respectively) were washed three times with methanol to remove excess ZIF-67 nanoparticles (NPs), and then dried using a freeze-drying method. For comparison, ZIF-67 nanoparticles (NPs) without an ANF film were also prepared under the same conditions (stored for about 3 hours).

[0088] Example 3 Preparation of HFN Composites. According to certain aspects of the present invention, HFN composites are prepared using chemical vapor deposition (CVD) technology, via a thermal annealing process of ANF@ZIF, using melamine as a precursor, without any additional catalyst. The ANF@ZIF composite is placed as a template in a ceramic boat associated with a certain amount of melamine (melamine / ANF@ZIF mass ratio of 10:1), and then annealed under a N2 atmosphere at 2°C / min. -1 The gradual heating rate resulted in carbonization at approximately 700°C for about 1 hour (see [reference]). Figure 7A – Figure 7D ).

[0089] Example 4 Material characterization. The morphologies of ANF, ANF@ZIF, and HFN were observed using scanning electron microscopy (SEM, FEI Nova Nanolab dual-beam FIB) and transmission electron microscopy (TEM, JEOL JEM-2010, operating voltage 200 kV). X-ray diffraction patterns (XRD, D / Max-2550 PC rotating anode X-ray generator, Cu Ka radiation between approximately 5° and 60°, scan rate 2° / min), Raman spectroscopy (WITEC Alpha 300 S micro Raman system equipped with a 488 nm laser under ambient conditions), X-ray photoelectron spectroscopy (XPS, RBD upgraded PHI-5000C ESCA with monochromatic Al Ka ​​(1486.6 eV) radiation), and thermogravimetric analysis (TGA, TA Instruments Discovery, operating at 30 mL / min in air atmosphere) were also performed. -1 At a flow rate of 10°C / min -1 The temperature was raised to 500°C. The specific surface area of ​​HFN was measured using the Brunauer-Emmett-Teller (BET) theory via nitrogen adsorption / desorption isotherms (Micromeritics ASAP 2020 V3.00 H). UV-Vis absorption spectroscopy was performed to evaluate the polysulfide adsorption capacity of conventional rGO and the HFN embodiment of this invention. Approximately 4 mg of rGO and HFN were placed in sealed Li₂S₄ solution vials (4 mL each, 0.1 mmol / L). -1 Pure Li₂S₄ solution was used as a reference. After 24 h of absorption, the UV-Vis absorption spectra of these solutions were measured using an Evolution 300 UV-Vis spectrophotometer with baseline correction. Li₂S₄ was prepared by the cis reaction of Li₂S (99.9%, Sigma-Aldrich) and sulfur (99.5%, Sigma-Aldrich) in a 1:3 molar ratio in a DOL / DME (v:v=1:1) solution.

[0090] Example 5 Electrochemical measurements were performed. Lithium trifluoromethanesulfonate (LiCF3SO3, 98%, Sigma-Aldrich, 1M) and LiNO3 (99%, Sigma-Aldrich, 2wt.%) were dissolved in DME (99%, Sigma-Aldrich) and DOL (99.5%, Sigma-Aldrich) (v:v=1:1) to prepare the electrolyte for the Li-S battery. The battery (standard CR2032 button cell) was prepared in an argon-filled glove box. Before battery assembly, the sulfur host of the HFN cathode was dried in a vacuum drying oven at 80°C for 12 hours. HFN was fabricated into sheets and used directly as the cathode, with an area of ​​1.0 cm × 1.0 cm.

[0091] Various sulfur cathodes were prepared to obtain CoCF@S, rGO@S, and HFN@S electrodes by dropping a 0.5 MS / CS2 solution into a prepared host matrix, followed by drying at approximately 60 °C for approximately 6 hours and heat treatment at approximately 155 °C for approximately 12 hours. The sulfur content of the conventional electrode was controlled at approximately 3.84 mg / cm². -2 By increasing the amount of S / CS2 solution, concentrations of 7.68, 11.52, 15.35, and 19.20 mg cm⁻¹ can also be prepared. -2 Higher sulfur content. CELGARD TM 2400 and pure lithium foil were used as separator and anode, respectively. The electrolyte contained a 1M LiTFSI DME / DOL (v:v=1:1) solution and 2 wt.% LiNO3 as an additive. The total electrolyte / sulfur ratio was controlled at 8:1 (μL mg). -1 Using a LAND-CT2001A battery tester at room temperature in constant current mode at 1.7–2.8 V (relative to Li / Li). + The assembled button cell was measured at different currents within a voltage range of 0.2C to 10C (1C = 1675 mAg). -1 The EIS was performed in the range of 100 kHz to 0.05 Hz, with a potential amplitude of 20 mV.

[0092] The binding energy (Eb) between HFN and LiPS was calculated using density functional theory (DFT) and is defined as follows:

[0093] Where E s+HFN E s and E HFNThese represent the energies of LiPS-HFN, LiPS, and HFN, respectively. The initial conformations of all molecules were obtained using molecular mechanics (MM) methods (Forcite module). DFT calculations were performed in the Dmol3 module of AccelrysMaterial Studio.

[0094] From transmission electron microscopy (TEM) images (see) Figure 2A – Figure 2E The growth of multi-walled N-CNTs with highly graphitized walls was observed, with outer diameters ranging from approximately 5 nm to approximately 10 nm and inner diameters of approximately 15 nm. Some randomly stacked carbon layers indicate the presence of more defects and edges within the N-CNTs (see...). Figure 2C (circular regions). A large number of 20 nm NPs were detected, particularly between N-CNTs. The 0.20 nm lattice spacing indicates that these regions were formed at high temperatures by Co in ZIF-67. 2+ Derivative Co (see Figure 2D and 2E This is consistent with XRD and Raman characterization.

[0095] NCZC exhibited 653 m 2 g -1 The high specific surface area and large pore volume of NCZC, with pore sizes mostly below 10 nm according to Brunauer-Emmett-Teller (BET) analysis, likely effectively enhance sulfur loading, electrolyte permeability, and the confinement and conversion of LiPS. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of Co and N in NCZC, with characteristic peaks at approximately 780 eV and 399 eV, respectively. From the C1s spectrum of NCZC (see...),... Figure 2F The presence of CN bonds confirms that N atoms have been successfully doped into the graphite domain. It is well known that N-doped carbon materials possess high electrical conductivity and a strong affinity for LiPS. Three types of N were observed in the N1s XPS peak: pyridine N (398.1 eV), graphitic N (400.8 eV), and oxide N (404.9 eV) (see [link to relevant documentation]). Figure 2G Undoubtedly, each N originates from the ANF network, ZIF-67, and the decomposition of melamine. Figure 2H The peak at 783.1 eV represents Co-N. x Species commonly detected in Co-containing N-doped carbon complexes. Co in NCZC 2p Co in the spectrum 2p1 / 2 (796.1 eV) and Co 2p3 / 2The presence of (780.4 eV) indicates that most Co exists in an oxidized state, primarily due to the oxidation of Co NPs in air. Thermogravimetric analysis (TGA) revealed that NCZC-3 contains approximately 25.3 wt.% Co. The abundant polar sites in this complex are expected to promote the redox kinetics of sulfur species within the porous carbon network and synergistically contribute to inhibiting the shuttle movement of soluble LiPS away from the cathode.

[0096] Inspired by the highly networked structure, NCZC was tested as a sulfur host for Li-S batteries and compared with rGO aerogel or CoCF-based batteries. All these batteries exhibited typical double-discharge plateau curves (see...). Figure 3A This is consistent with the formation of higher-order and lower-order LiPS. Notably, NCZC minimizes the potential difference between the discharge and charge curves of these different batteries, while also resulting in sharper peaks and less electrochemical polarization in cyclic voltammetry (CV), indicating favorable redox kinetics in the NCZC electrode. The galvanostatic cycling performance of batteries using different electrodes (see...) Figure 3B The NCZC battery is shown to provide 1351 mAh g. -1 Its high initial capacity surpasses that of state-of-the-art rGO-based sulfur host systems (1192 mAh g). -1 It also exceeds the capacity of CoCF series batteries (1296 mAhg). -1 This means that sulfur utilization is significantly improved due to the layered multi-scale design. For the NCZC cathode, 1205 mAh g⁻¹ was achieved after more than 100 cycles. -1 Its high capacity retention and near 99% coulombic efficiency (CE) indicate superior operational durability compared to other sulfur-hosted designs (for CoCF electrodes, 970 mAh g⁻¹). -1 CE: 97%; for rGO electrode, 832 mAhg -1 (CE: 92%). Impressively, for NCZC series batteries, the shape of the charge / discharge curve hardly changes from the 1st to the 100th cycle (see [link]). Figure 6 This indicates that the multi-scale design effectively confined LiPS diffusion and stabilized the sulfur redox reaction. The functional advantages of NCZC in terms of higher initial discharge capacity, lower potential difference, and longer operating durability are attributed to its structure—a highly porous, conductive network of carbonized ANF and CNTs complementing each other. The morphology of the NCZC electrode was further characterized to evaluate its structural stability during cycling. After 100 cycles, the hierarchical nanofiber structure remained intact without decomposition, demonstrating the significant structural stability of NCZC during battery cycling.

[0097] Further various rate and long-term cycling tests were conducted to investigate its rate performance and cycling performance (see [link to relevant documentation]). Figure 3C – Figure 3G Even at high current densities up to 10C, NCZC batteries can still provide close to approximately 600 mAh g. -1 It exhibits highly reversible capacity and rapidly recovers to approximately 1040 mAhg when the current density switches back to 0.5C. -1 This indicates rapid charge transport and rapid charge transport to sulfur. Although the voltage plateau decreases on the discharge curve at high current densities, the tilt shape remains almost unchanged (see...). Figure 3D This further confirms the rapid sulfur redox conversion in NCZC-based batteries. The Nyquist plot also further supports this conclusion (see...). Figure 3E The semicircle in the high-frequency region of the NCZC electrode is much smaller than that of the rGO and CoCF electrodes due to its lower charge transfer resistance. Conversely, the rGO and CoCF batteries exhibit approximately 302 mAh g⁻¹ at a high current density of 10C. -1 and approximately 420 mAhg -1 Much lower capacity (see) Figure 3C Equally important, NCZC batteries also exhibit excellent cycle life, exceeding 2500 cycles with a negligible capacity decay of 0.011% per cycle, and a coulombic efficiency (CE) consistently above 98% at a current rate of 1.0C (see [link to relevant documentation]). Figure 3G It is worth noting that the rate performance, cycle life, and capacity retention of the corresponding NCZC cells are superior to those of previously reported representative MOF-derived or carbon-based sulfur host electrodes (see [link to relevant documentation]). Figure 3F (as well as Tables 1 and 2), which strongly supports the advantages of NCZC as an advanced sulfur host in Li-S battery cathodes.

[0098] Table 1 compares the rate performance and long-term cycling performance of the HFN electrode with a representative sulfur electrode based on a MOF-derived carbon host.

[0099]

[0100] BHPC: Bicontinuous hierarchical porous carbon; CPZC: Tubes on cubic carbon hybrids; HPTCF: Hollow carbon polyhedra embedded in tubular carbon fibers; NDC: Nitrogen-doped carbon; N-ZDC: N-doped ZIF-8 derived carbon nanospheres; HPCN: Porous carbon nanoplates; AMCP: Activated mesoporous carbon polyhedra; ISCF: Self-supporting conductive framework; NSHPC: N, S co-doped hollow porous carbon shells; CHPCF: Cross-linked hierarchical porous carbon fibers; FMNCN: Flower-shaped microporous nitrogen-doped carbon nanosheets; FLHPC: French fry-shaped hierarchical porous carbon; MPCN: Micro / mesoporous carbon nanorods; rGO: Reduced graphene oxide; GO: Graphene oxide; CNT: Carbon nanotubes; NS: Nanosheets; MWCNT: Multi-walled carbon nanotubes; Meso: Mesoporous; GC: Graphitic carbon; PC: Porous carbon.

[0101] Table 2 Comparison of electrochemical performance of various carbon-based cathodes in lithium-sulfur batteries

[0102] To provide a quantitative description, the chemisorption of LiPS by NCZC was evaluated using density functional theory (DFT) calculations (see [link to DFT]). Figure 4A and Figure 4B Compared to the weak binding of higher-order LiPSs (such as Li₂S₈, Li₂S₆, and Li₂S₄) to rGO, they bind more strongly to NCZC (see [link to relevant documentation]). Figure 4A and Figure 4B (and Table 3), which makes chemical trapping of LiPS possible, thereby preventing its transport to the lithium anode.

[0103] Table 3 shows the calculated binding energies of Li-S species with C-Co-N and N-doped carbons from HFN and rGO, respectively.

[0104]

[0105] For lower-order LiPSs (such as Li₂S₂ and Li₂S), the binding energy is even higher, which is crucial for preventing LiPS cross-linking and for superiority over rGO. Using LiPS colorimetry, the theoretical prediction of NCZC's affinity for LiPS was experimentally confirmed. After dispersing rGO and NCZC in a Li₂S₄ solution for approximately 24 hours, NCZC showed a much lighter color than rGO (see [link to LiPS colorimetry]). Figure 4C ), and S4 observed in the ultraviolet-visible spectrum 2- The weaker peak at 415 nm is consistent (see...) Figure 4C The adsorption of chemical polysulfides was further evaluated by XPS analysis (see...). Figure 4D Specifically, in the S of Li2S4 2pTwo pairs of typical binding energies were observed in the spectrum at approximately 161.5 eV and approximately 162.8 eV, which are attributed to terminal sulfur (S₂) groups, respectively. T -1 ) and bridging sulfur (SB) 0 Upon contact with NCZC, these peaks shift slightly to higher binding energy ranges, indicating a decrease in electron cloud density in sulfur atoms due to chemical interactions between Li₂S₄ and NCZC. Simultaneously, two new pairs of peaks appear in the high binding energy range, corresponding to sulfite and sulfate, representing the interactions between polysulfides and oxides in NCZC. Another new peak appears at 160.5 eV, originating from CoS binding, indicating the interaction between polysulfides and Co sites. Furthermore, due to the formation of Li-N bonds, Li… 1s The spectrum showed broadened peaks after absorption by NCZC, and a new sub-peak appeared at 55.7 eV (see [link to NCZC absorption spectrum]). Figure 4E This is consistent with the XPS analysis results mentioned above. These changes in the XPS spectra collectively demonstrate the strong chemisorption capacity of NCZC for LiPS, thereby chemically enhancing the limitations of electroactive materials in Li-S batteries.

[0106] To obtain cathode materials more compatible with high energy density and expanded commercial battery manufacturing processes, cathodes with 7.68, 11.52, 15.36, and 19.20 mg cm⁻¹ were also prepared. -2 NCZC sulfur host with high area sulfur loading and a controlled E / S ratio of 8:1. Sulfur loading was 15.36 mg / cm³. -2 The battery still exhibits a high performance of 17.0 mAh cm⁻¹ after 50 charge / discharge cycles. -2 Reversible area capacity (see) Figure 5A Its performance surpasses that of most state-of-the-art sulfur hosts designed specifically for high sulfur loads (see...). Figure 5B (and Table 4) as well as commercial lithium-ion batteries.

[0107] Table 4 compares the areal capacity of HFN with recently published data exceeding 5 mg / cm². -2 The areal capacity of high sulfur-loaded Li-S batteries was compared.

[0108]

[0109] The sulfur loading was further increased to 19.2 mg cm⁻¹ -2 This results in limited capacity gains because electron / ion transfer is hindered. At high current densities of 5C, the sulfur content reaches approximately 15.36 mg cm⁻¹. -2 The NCZC battery achieves approximately 9.9 mAh / cm³. -2 (642.8 mAhg)-1 High reversible capacity (see) Figure 5C and Figure 5D When the charge / discharge rate was switched back to 0.5C, a rapid increase in capacity was observed to approximately 15.8 mAh / cm³. -2 (1023.3 mAhg -1 ). Figure 5E Cyclic performance tests showed that the NCZC electrode maintained approximately 10.2 mAh / cm³ after 200 cycles at 0.2 C. -2 The high reversible areal capacity of (662.3 mAhg⁻¹) and the low capacity decay rate of 0.20% also indicate that the cycling stability and capacity retention are significantly improved compared with other sulfur hosts.

[0110] In some variants, highly efficient sulfur-modified host materials with a layered structure include a carbon fiber aerogel framework, Co-embedded, N-doped porous carbon coupled with a large number of N-doped carbon nanotubes. Benefiting from the enhanced conductivity of the nitrogen-doped carbon substrate, shuttle phenomenon suppressed by the strong binding affinity between polysulfides and polar active sites, sulfur redox kinetics promoted by a sufficient electrode / electrolyte interface, and the greater tolerance of the porous structure to volume changes, the constructed sulfur host materials exhibit excellent rate performance up to 10C, significant cycle durability exceeding 2500 cycles, and an ultra-low capacity decay of 0.011% per cycle at 15.36 mg cm⁻¹. -2 17.0 mAhcm under high sulfur loading -2 Its high reversible specific capacity / area capacity and electrolyte-saving properties demonstrate its great potential in Li-S batteries.

[0111] In summary, this disclosure provides a novel porous network for the cathode of high-performance Li-S batteries by addressing many inherent problems faced by conventional sulfur-hosted materials. The well-defined 3D hierarchical hybrid architecture creates a conductive network with a hierarchical scale that facilitates electron / ion transport, while the highly porous structure with abundant active Co and N sites exposes interfaces for LiPS capture and facilitates sulfur redox kinetics. Furthermore, the N-CNTs grown on the porous carbon not only provide additional nitrogen (N) polar sites for the chemical anchoring of lithium polysulfides (LiPSs) but also interconnect adjacent 3D nanofiber frameworks to enhance structural integrity and provide high-rate charge transport throughout the electrode. Due to these unique and synergistic advantages, the NCZC prepared according to certain aspects of the invention provides a sulfur-hosted material for the cathode, exhibiting fast reaction kinetics, high sulfur utilization, excellent rate performance, and ultra-long cycle life, with very low capacity decay under both low and high sulfur loadings, and electrolyte conservation. This disclosure provides a novel approach to designing cathode structures and chemical interactions of active materials to achieve high energy density and long lifespan Li-S batteries for practical applications, as well as for other energy storage devices such as supercapacitors, metal-ion or metal-air batteries.

[0112] The foregoing description of the embodiments has been provided for illustrative and descriptive purposes. It is not intended to be exhaustive or limiting of this disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but are interchangeable where applicable and can be used in selected embodiments, even if not specifically shown or described. Variations are also possible in many respects. Such variations should not be considered a departure from this disclosure, and all such modifications are intended to be included within the scope of this disclosure.

Claims

1. An electrode material comprising: a sulfur electroactive material; and a sulfur host material configured to receive the sulfur electroactive material, the sulfur host material comprising: a fibrous carbonaceous network; an electroactive metal associated with the fibrous carbonaceous network; and a plurality of carbon nanotubes formed on the fibrous carbonaceous network.

2. The electrode material of claim 1, wherein, The electroactive metal comprises a transition metal.

3. The electrode material of claim 2, wherein, The transition metal comprises cobalt.

4. The electrode material of claim 1, wherein, The electroactive material is adsorbed on a surface of the fibrous carbonaceous network.

5. The electrode material of claim 1, wherein, The electroactive material is intercalated in the fibrous carbonaceous network.

6. The electrode material of claim 1, wherein, The electroactive material is adsorbed on a surface of the fibrous carbonaceous network and intercalated in the fibrous carbonaceous network.

7. The electrode material of claim 1, wherein, The plurality of carbon nanotubes are formed on the fibrous carbonaceous network at sites of the electroactive metal.

8. The electrode material of claim 1, wherein, The plurality of carbon nanotubes are nitrogen-doped.

9. The electrode material of claim 1, wherein, The electrode material has an area capacity greater than or equal to about 17 mAh cm -2 .

10. The electrode material of claim 1, wherein, The electrode material has a sulfur loading greater than or equal to about 15 mg / cm 2 .

11. A lithium-sulfur electrochemical cell comprising: a positive electrode, the positive electrode comprising: a sulfur electroactive material; and a sulfur host material configured to receive the sulfur electroactive material, the sulfur host material comprising: a fibrous carbonaceous network, an electroactive metal associated with the fibrous carbonaceous network, and a plurality of carbon nanotubes formed on the fibrous carbonaceous network, a negative electrode, the negative electrode comprising lithium; a separator disposed between the positive electrode and the negative electrode; and an electrolyte incorporated into at least one of the positive electrode, the negative electrode, and the separator.

12. The lithium-sulfur electrochemical cell of claim 11, wherein, The electroactive metal comprises a transition metal.

13. The lithium-sulfur electrochemical cell of claim 11, wherein, The electroactive material is adsorbed on a surface of the fibrous carbonaceous network, the electroactive material is intercalated in the fibrous carbonaceous network, or the electroactive material is adsorbed on a surface of the fibrous carbonaceous network and intercalated in the fibrous carbonaceous network.

14. The lithium-sulfur electrochemical cell of claim 11, wherein, The plurality of carbon nanotubes are formed on the fibrous carbonaceous network at sites of the electroactive metal.

15. The lithium-sulfur electrochemical cell of claim 11, wherein, The plurality of carbon nanotubes are nitrogen-doped.

16. The lithium-sulfur electrochemical cell of claim 11, wherein, The area capacity of the positive electrode is greater than or equal to about 17 mAh cm -2 and the sulfur loading is greater than or equal to about 15 mg / cm 2 .

17. The lithium-sulfur electrochemical cell of claim 11, wherein, The lithium-sulfur electrochemical cell has an electrolyte-to-sulfur ratio (E / S) of less than or equal to about 8:

1.

18. A method of manufacturing an electrode for a lithium-sulfur electrochemical cell, the method comprising: pyrolyzing a porous membrane formed from a plurality of aramid nanofibers and comprising a plurality of metal-organic framework nanoparticles to form a fibrous carbonaceous network; incorporating a transition metal into the fibrous carbonaceous network; and forming a plurality of carbon nanotubes on a plurality of sites in the fibrous carbonaceous network associated with the transition metal to form a sulfur host material configured to receive a lithium-sulfur electroactive material that cycles lithium ions.

19. The method of claim 18, wherein, The method further comprises: forming the porous membrane by spin coating the plurality of aramid nanofibers and incorporating the plurality of metal-organic framework nanoparticles therein.

20. The method of claim 18, wherein, The metal-organic framework nanoparticles comprise a plurality of zeolitic imidazolate framework-67 (ZIF-67) particles and the transition metal comprises cobalt.

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