Lithium-sulfur battery cathodes and methods for making

Abstract

Lithium-sulfur battery cathodes including one or more porous carbon layers of rigid porous carbon agglomerates of predetermined average particle diameter. The rigid porous carbon agglomerates may include catalyst nanoparticles. The catalyst nanoparticles anchor lithium-polysulfide intermediates at the cathode and mitigate loss of sulfur from the cathode. The rigid porous carbon agglomerates provide for dense packing of carbons at the cathode with a cathode loading of at least 7 mg / cm2 based on the total weight of carbonaceous materials, sulfur, binder, and other materials that are typically loaded on a cathode substrate.

Description

LITHIUM-SULFUR BATTERY CATHODES AND METHODS FOR MAKINGRELATED APPLICATIONS

[0001] This Patent Application claims priority to U.S. Provisional Patent Application No. 63 / 469,588 entitled “LITHIUM-SULFUR BATTERY CATHODES AND METHODS FOR MAKING” and filed on May 30, 2023, to U.S. Provisional Patent Application No.63 / 541,708 entitled “LITHIUM-SULFUR BATTERY CATHODES AND METHODS FOR MAKING” and filed on September 29, 2023, and to U.S. Provisional Patent Application No. 63 / 652,761 entitled “LITHIUM-SULFUR BATTERY CATHODES AND METHODS FOR MAKING” and filed on May 29, 2024, all of which are assigned to the assignee hereof. The disclosures of all prior Applications are considered part of and are incorporated by reference in this Patent Application in their respective entireties.TECHNICAL FIELD

[0002] This disclosure relates generally to batteries, and, more particularly, to lithiumsulfur batteries that can compensate for operational cycle losses.DESCRIPTION OF RELATED ART

[0003] Recent developments in batteries allow consumers to use high-capacity batteries such as Li-sulfur batteries in many new applications. However, further improvements in battery technology are desirable.SUMMARY

[0004] This Summary is provided to introduce in a simplified form a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0005] In some implementations, a lithium-sulfur battery cathode may include a cathode substrate and one or more porous carbon layers disposed on the cathode substrate. The one or more porous carbon layers may include rigid porous carbon agglomerates of porous carbon primary nanoparticles, catalyst nanoparticles dispersed in the rigid porous carbon agglomerates, carbonized binder residue dispersed in the rigid porous carbon agglomerates,and sulfur dispersed in the rigid porous carbon agglomerates. In some implementations, the porous carbon primary nanoparticles may include an inner porous shell disposed about a center of the porous carbon primary nanoparticles and enclosing an inner porous carbon region, an outer porous shell enclosing an outer porous carbon region disposed between the inner shell and outer shell, and an interconnected porous network disposed in and in fluid communication with the inner and outer carbon regions. The inner carbon region and outer carbon region may be characterized by an average pore size and an average pore density associated with each region. In some aspects, the average pore size may decrease along a radial direction from the center to the outer porous shell.

[0006] In some aspects, the porous carbon primary nanoparticles may further include one or more intermediate porous shells disposed between the inner porous shell and the outer porous shell, wherein each of the intermediate porous shells encloses a respective intermediate porous carbon region. In some aspects, the rigid porous carbon agglomerates may include three-dimensional graphene layers. In some aspects, the rigid porous carbon agglomerates may include few layer graphene (FLG) nanoplatelets orthogonally joined to each other in a three-dimensional (3D) porous graphene scaffold structure. The rigid porous carbon agglomerates may be characterized by a Raman spectroscopy signature with an ID / IG ratio between approximately 0.95 and approximately 1.05.

[0007] In some implementations, the catalyst nanoparticles may be metal-based or non- metal based. In some aspects, the catalyst nanoparticles may include one or more of metal, metal oxide, metal carbide, metal nitride, or any combination thereof. The catalyst nanoparticles may be dispersed in one or more of the external surfaces of the rigid porous carbon agglomerates, or within the rigid porous carbon agglomerates. In some aspects, the catalyst nanoparticles may include MgO nanoparticles. The average size of the MgO nanoparticles may be less than approximately 200 nm. The loading of the MgO nanoparticles in the rigid porous carbon agglomerates may be between approximately 10 wt% and approximately 20 wt%. In some aspects, the loading of the MgO nanoparticles in the rigid porous carbon agglomerates may be between approximately 1 wt% and approximately 50 wt%.

[0008] Without being bound by any particular theory, the selection of the polymeric binder may impact the dispersion of the metal-based nanoparticles and the size of the metalbased nanoparticles in the rigid porous carbon agglomerates. In some implementations, the catalyst nanoparticles may include tungsten carbide (WC) nanoparticles. An average size ofthe WC nanoparticles may be between approximately 100 nm and 500 nm. The loading of the WC nanoparticles in the rigid porous carbon agglomerates may be between approximately 10 wt% and approximately 20 wt%. In some aspects, the loading of the WC nanoparticles in the rigid porous carbon agglomerates may be between approximately 1 wt% and approximately 50 wt%. In some implementations, the carbonized binder residue in the rigid porous carbon agglomerates may correspond to calcined byproducts of one or more of styrene butadiene rubber, vinyl polymers, polyvinylidene fluoride, poly acrylic acid (“PAA”), carboxyl methyl cellulose, polyvinylpyrrolidone, polyvinyl acetate, polyacrylonitrile (“PAN”), polyethyleneimine (“PEI”), polymethylmethacrylate (“PMMA”), pitch, or formaldehyde-based resins.

[0009] In some implementations, the sulfur to carbon weight ratio in the one or more one or more porous carbon cathode layers may be between approximately 1:5 and 10:1. The packing density of the one or more porous carbon cathode layers may be at least 7 mg / cm2. The thickness of the one or more porous carbon cathode layers may be between approximately 10 pm and approximately 200 pm. The average size of the porous primary carbon nanoparticles in the rigid porous carbon agglomerates may be between approximately 20 nm and approximately 50 nm. The average size of the rigid porous carbon agglomerates may be between approximately 50 nm and approximately 500 nm. An average size of the rigid porous carbon agglomerates may be at least 1 pm.

[0010] In some implementations, the rigid porous carbon agglomerates may further include one or more of a lithium-ion conducting film or an electron conducting film disposed on the surface of the rigid porous carbon agglomerates. In some aspects, the lithium-ion conducting film includes one or more of lithium lanthanum zirconium oxide (“LLZO”), lithium 3-glycidyloxypropanesulfonate (“LiGPS”), lithium bis(trifluoromethanesulfonyl)imide (“LiTFSI”), lithium phosphorus oxynitride (“LiPON”), or any combination thereof.

[0011] In some implementations, an example lithium- sulfur battery may include a lithium anode any one of the previously described example cathodes disposed opposite to the anode and a fluorinated ether electrolyte disposed between and in contact with the anode and the cathode. The electrolyte may include one or more of lithium nitrate (LiNOs) or lithium bis(trifluoromethanesulfonyl)imide (“LiTFSI”) dissolved in mixtures of one or more of 1,2- dimethoxyethane (“DME”), 1,3-dioxolane (“DOL”), bis (2,2,2-trifluoroethyl) ether (“BTFE”) or 1,1,2,2-tetraethoxyethane (“TEE”). The example lithium-sulfur battery may furtherinclude a separator disposed between the anode and the cathode. In some aspects, the separator may include a microporous monolayer polypropylene membrane. In some aspects, the separator may include a ceramics-coated material.

[0012] In some implementations, the geometrical shape of the lithium- sulfur battery may be cylindrical. An example cylindrical battery may be approximately 18 mm in diameter and approximately 65 mm in length. In some aspects, the cylindrical battery may be approximately 21 mm in diameter and approximately 70 mm in length. In some aspects, the cylindrical battery may be approximately 46 mm in diameter and approximately 80 mm in length. In some implementations, an example method for fabricating a lithium-sulfur battery cathode may include dispersing agglomerates of porous primary carbon nanoparticles in a solution including a catalyst precursor and one or more polymeric binders, spray drying the agglomerates dispersed in the solution, and calcining the spray dried agglomerates at between approximately 800 °C and approximately 1200 °C to form rigid porous carbon agglomerates including dispersed catalyst nanoparticles and dispersed carbonized binder residue. The calcining process may be conducted in the presence of argon, or a mixture of compressed dry air and one or more of argon or nitrogen, or argon and hydrogen gas mixture. The example method may further include surface etching the agglomerates of porous carbon nanoparticles prior to the dispersing step. Surface etching may include one or more of CO2 etching, potassium hydroxide (KOH) etching, zinc chloride (ZnCh) etching or nitric acid (HNO3) etching. The example method may further include producing carbon-sulfur composites (“CSC”) including the rigid porous carbon aggregates. The example method may further include casting a slurry including the carbon-sulfur composites as one or more layers on a cathode substrate. The amount of one or more polymeric binders in the solution may be between approximately 5 wt% and approximately 20 wt% of the weight of the agglomerates.

[0013] In some implementations, an example method for fabricating a lithium-sulfur battery cathode may further include dispersing the carbon-sulfur composites in a solution including one or more lithium-ion conducting salts or electron conducting salts, spray drying the carbon-sulfur composites dispersed in the solution to form carbon-sulfur composites having one or more of a lithium-ion conducting film or an electron conducting film disposed on the surface of the rigid porous carbon agglomerates, and casting a slurry including the carbon-sulfur composites including one or more of a lithium-ion conducting film or an electron conducting film as one or more layers on a cathode substrate. In some aspects, lithium-ion conducting salts may include one or more of lithium lanthanum zirconium oxide(“LLZO”), lithium 3-glycidyloxypropanesulfonate (“LiGPS”), lithium bis(trifluoromethanesulfonyl)imide (“LiTFSI”), lithium phosphorus oxynitride (“LiPON”), or any combination thereof.

[0014] In some implementations, an example carbon material may include rigid porous carbon agglomerates of porous primary carbon nanoparticles, catalyst nanoparticles dispersed in the rigid porous carbon agglomerates, and carbonized binder residue dispersed in the rigid porous carbon agglomerates, wherein the catalyst nanoparticles are dispersed in one or more of the external surfaces of the agglomerates, or within the agglomerates. The rigid porous carbon agglomerates may include few-layer graphene (“FLG”) nanoplatelets orthogonally joined to each other in a three-dimensional (3D) porous graphene scaffold structure. The catalyst nanoparticles may include one or more of metal, metal oxide, metal carbide, metal nitride, or any combination thereof. The carbonized binder residue may further include trace amounts of nitrogen. The carbonized binder residue may correspond to calcined byproducts of one or more of styrene butadiene rubber, vinyl polymers, poly vinylidene fluoride, poly acrylic acid (“PAA”), carboxyl methyl cellulose, polyvinylpyrrolidone, polyvinyl acetate, polyacrylonitrile (“PAN”), polyethyleneimine (“PEI”), polymethylmethacrylate (“PMMA”), pitch, or formaldehyde-based resins.

[0015] In some implementations, an example carbon material may include rigid porous carbon agglomerates of any one of the porous carbon primary nanoparticles disclosed herein and carbonized binder residue dispersed in the rigid porous carbon agglomerates, wherein the rigid porous carbon agglomerates may resist deformation at shear rates of at least 500 s'1during mixing of a slurry including the rigid porous carbon agglomerates in a high shear mixer. The carbonized binder residue may correspond to calcined byproducts of one or more of styrene butadiene rubber, vinyl polymers, polyvinylidene fluoride, poly acrylic acid (PAA), carboxyl methyl cellulose, polyvinylpyrrolidone, polyvinyl acetate, polyacrylonitrile (PAN), polyethyleneimine (PEI), polymethylmethacrylate (PMMA), pitch, or formaldehyde- based resins. The rigid porous carbon agglomerates may include catalyst nanoparticles dispersed in the rigid porous carbon agglomerates. The catalyst nanoparticles may include one or more of metal, metal oxide, metal carbide, metal nitride, or any combination thereof.

[0016] In some implementations, a method for fabricating a lithium-sulfur battery cathode may include dispersing agglomerates of porous carbon primary nanoparticles in a solution including a catalyst precursor and one or more polymeric binders to form a slurry, carbonizing the slurry at a temperature of at least 500 °C to form carbon-based pellets, andmilling the carbon-based pellets to form rigid porous carbon agglomerates including catalyst nanoparticles and carbonized binder residue dispersed in the rigid porous carbon agglomerates. The porous carbon primary nanoparticles may include an inner porous shell disposed about a center of the porous primary carbon nanoparticles and enclosing an inner porous carbon region, an outer porous shell enclosing an outer porous carbon region disposed between the inner shell and outer shell, and an interconnected porous network disposed in and in fluid communication with the inner and outer carbon regions. The inner carbon region and outer carbon region may be characterized by an average pore size and an average pore density associated with each region. The average pore size may decrease along a radial direction from the center to the outer porous shell.

[0017] In some implementations, a cathode associated with a lithium-sulfur battery may include a cathode substrate and one or more porous carbon layers disposed on the cathode substrate. The one or more porous carbon layers may include rigid porous carbon agglomerates of porous carbon primary nanoparticles. In some implementations, one or more of sulfur or carbonized binder residue may be dispersed in the rigid porous carbon agglomerates. In some other implementations, the average particle diameter of the rigid porous carbon agglomerates (dso percentile) may be greater than a threshold average particle diameter.

[0018] In some implementations, the threshold average particle diameter may be approximately 15 pm. In some aspects, a packing density of the one or more porous carbon layers may be at least 7 mg / cm2. In some other aspects, a thickness of the one or more porous carbon layers may be between approximately 20 pm and approximately 200 pm.

[0019] In some implementations, the porous carbon primary nanoparticles may include an inner porous shell disposed about a center of the porous carbon primary nanoparticles and enclosing an inner porous carbon region, an outer porous shell enclosing an outer porous carbon region disposed between the inner shell and the outer shell, and an interconnected porous network disposed in and in fluid communication with the inner and outer carbon regions. In some aspects, the inner carbon region and the outer carbon region may be characterized by an average pore size and an average pore density associated with each region. In some other aspects, the average pore size may decrease along a radial direction from the center to the outer porous shell. In some instances, the porous carbon primary nanoparticles may further include one or more intermediate porous shells disposed betweenthe inner porous shell and the outer porous shell. Each of the intermediate porous shells may enclose a respective intermediate porous carbon region.

[0020] In some implementations, the rigid porous carbon agglomerates may be characterized by an electrical conductivity of between approximately 500 S / m and 20,000 S / m when compressed at a pressure of approximately 12,000 pounds per square inch (psi). In some other implementations, a sulfur to carbon weight ratio in the one or more one or more porous carbon layers may be between approximately 1:5 and 10:1. In some implementations, the rigid porous carbon agglomerates may be characterized by a Raman spectroscopy signature with an ID / IG ratio between approximately 0.95 and approximately 1.05.

[0021] In some implementations, the carbonized binder residue may correspond to calcined byproducts of one or more of styrene butadiene rubber, vinyl polymers, polyvinylidene fluoride, poly acrylic acid (“PAA”), carboxyl methyl cellulose, polyvinylpyrrolidone, polyvinyl acetate, polyacrylonitrile (“PAN”), polyethyleneimine (“PEI”), polymethylmethacrylate (“PMMA”), pitch, or formaldehyde-based resins.

[0022] In some implementations, the rigid porous carbon agglomerates may include catalyst nanoparticles dispersed within the rigid porous carbon agglomerates. In some aspects, the catalyst nanoparticles may include MgO nanoparticles.

[0023] In some implementations, a method for fabricating a cathode associated with a lithium-sulfur battery may include dispersing agglomerates of porous primary carbon nanoparticles in a solution including one or more polymeric binders, spray drying the agglomerates dispersed in the solution, and forming rigid porous carbon agglomerates including dispersed carbonized binder residue by calcining the spray dried agglomerates at between approximately 800 °C and approximately 1200 °C. In some other implementations an average particle diameter of the rigid porous carbon agglomerates (dso percentile) may be greater than a threshold average particle diameter. In some implementations, the threshold average particle diameter may be approximately 15 pm.

[0024] In some implementations, an example method for fabricating a cathode associated with a lithium-sulfur battery may further include producing carbon-sulfur composites (“CSC”) including the rigid porous carbon agglomerates. In some other implementations, an example method may further include casting a slurry including the carbon-sulfur composites as one or more porous carbon layers on a cathode substrate. In some implementations, the rigid porous carbon agglomerates may resist deformation at shear rates of at least 500 s'1during mixing of the slurry including the rigid porous carbon agglomerates in a high shear mixer.

[0025] Details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions of the following figures may not be drawn to scale.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1A shows a scanning electron microscope (“SEM”) image of rigid porous carbon agglomerates of porous carbon primary nanoparticles including catalyst nanoparticles, according to some implementations.

[0027] Figure IB shows a schematic diagram of rigid porous carbon agglomerates of porous carbon primary nanoparticles including catalyst nanoparticles, according to some implementations .

[0028] Figure 2A shows a SEM image of rigid porous carbon agglomerates of porous carbon primary nanoparticles including MgO nanoparticles, according to some implementations .

[0029] Figure 2B shows a cross sectional SEM image of rigid porous carbon agglomerates of porous carbon primary nanoparticles including MgO nanoparticles, according to some implementations.

[0030] Figures 2C-2D show transmission electron microscopy (TEM) images of rigid porous carbon agglomerates of porous carbon primary nanoparticles including MgO nanoparticles, according to some implementations.

[0031] Figure 3A shows a thermogravimetric analysis (TGA) graph of rigid porous carbon agglomerates of porous carbon primary nanoparticles including MgO nanoparticles, according to some implementations.

[0032] Figure 3B shows an X-ray diffraction (XRD) pattern of rigid porous carbon agglomerates of porous carbon primary nanoparticles including MgO nanoparticles, according to some implementations.

[0033] Figures 3C-3D show plots illustrating cathode discharge capacity and capacity retention in lithium- sulfur coin cells with cathodes including MgO catalyst nanoparticles in rigid porous carbon agglomerates, according to some implementations.

[0034] Figure 3E shows cyclic voltammetry curves of a lithium-sulfur cell with a cathode including MgO nanoparticles in rigid porous carbon agglomerates, according to some implementations .

[0035] Figure 4A shows a SEM image of example rigid porous carbon agglomerates of porous carbon primary nanoparticles including tungsten carbide (WC) nanoparticles, according to some implementations.

[0036] Figures 4B-4E show SEM-energy dispersive X-ray spectroscopy (EDS) elemental dispersion images of rigid porous carbon agglomerates of porous carbon primary nanoparticles including tungsten carbide (WC) nanoparticles, according to some implementations .

[0037] Figure 5A shows a SEM image of rigid porous carbon agglomerates of porous carbon primary nanoparticles including tungsten carbide (WC) nanoparticles, according to some implementations.

[0038] Figures 5B-5E show SEM-EDS elemental dispersion images of rigid porous carbon agglomerates of porous carbon primary nanoparticles including tungsten carbide (WC) nanoparticles, according to some implementations.

[0039] Figure 6A shows a SEM image of rigid porous carbon agglomerates of porous carbon primary nanoparticles including tungsten carbide (WC) nanoparticles, according to some implementations.

[0040] Figures 6B-6E show SEM-EDS elemental dispersion images of rigid porous carbon agglomerates of porous carbon primary nanoparticles including tungsten carbide (WC) nanoparticles, according to some implementations.

[0041] Figure 7A shows an example X-ray diffraction (XRD) pattern of rigid porous carbon agglomerates of porous carbon primary nanoparticles including WC nanoparticles, according to some implementations.

[0042] Figure 7B show a plot illustrating cathode discharge capacity of lithium-sulfur coin cells with cathodes including WC catalyst nanoparticles in rigid porous carbon agglomerates, according to some implementations.

[0043] Figure 8A shows a schematic diagram of an example porous carbon primary nanoparticle, according to some implementations.

[0044] Figure 8B depicts a TEM image showing aggregates of porous carbon primary nanoparticles, according to some implementations.

[0045] Figure 8C depicts a TEM image of agglomerates of porous carbon primary nanoparticles, according to some implementations.

[0046] Figure 8D shows a TEM image of surface etched agglomerates of porous carbon primary nanoparticles, according to some implementations.

[0047] Figure 9 shows a schematic diagram of another example porous carbon primary nanoparticle, according to some implementations.

[0048] Figure 10A shows an illustrative flowchart depicting an example operation for producing a lithium- sulfur battery cathode including rigid porous carbon agglomerates, according to some implementations.

[0049] Figure 10B shows schematic diagrams of rigid porous carbon agglomerates including ion or electron conducting surface coating, according to some implementations.

[0050] Figure 10C shows an illustrative flowchart depicting another example operation for producing a lithium- sulfur battery cathode including rigid porous carbon agglomerates, according to some implementations.

[0051] Figure 10D shows a plot illustrating an increase in adhesion of the cathode layers to the cathode substrate as a function of the density of one or more cathode layers of rigid porous carbon agglomerates, according to some implementations.

[0052] Figure 11 A shows a schematic diagram of a mesoporous carbon nanoparticle, according to some implementations. .

[0053] Figure 1 IB shows a SEM micrograph of agglomerates of porous carbon primary nanoparticles, according to some implementations.

[0054] Figure 12 shows a schematic diagram depicting an example lithium- sulfur cylindrical battery, according to some implementations.

[0055] Figure 13A shows a schematic diagram of a lithium-sulfur battery cathode including one or more porous carbon layers of rigid porous carbon agglomerates, according to some implementations.

[0056] Figure 13B shows a schematic diagram of a lithium- sulfur battery cathode including one or more porous carbon layers of rigid porous carbon agglomerates, according to some implementations.

[0057] Figure 13C shows a plot illustrating the effect of average particle diameter of rigid porous carbon agglomerates on capacity retention in lithium- sulfur coin cells, according to some implementations.

[0058] Figure 14 shows an illustrative flowchart of an example single-step operation for producing a lithium- sulfur battery cathode including rigid porous carbon agglomerates of predetermined average particle diameter, according to some implementations.

[0059] Figure 15 shows a plot illustrating the effect of spray dryer atomizing gas flow rate on the average particle diameter of rigid porous carbon agglomerates, according to some implementations .

[0060] Figures 16A-16B show plots illustrating the effect of average particle diameter of rigid porous carbon agglomerates on cathode discharge capacity and capacity retention in lithium-sulfur coin cells, according to some implementations.

[0061] Figure 17 shows a plot illustrating cathode discharge capacity in lithium-sulfur pouch cells with cathodes including WC catalyst nanoparticles in rigid porous carbon agglomerates, according to some implementations.

[0062] Like reference numbers and designations in the various drawings indicate like elements.DETAILED DESCRIPTION

[0063] The following description is directed to some example implementations for the purpose of describing the innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The described implementations can be implemented in batteries for a variety of applications and may be tailored to compensate for various performance related deficiencies. As such, the disclosed implementations are not to be limited by the examples provided herein, but rather encompass all implementations contemplated by the attached claims. Additionally, well-known elements of the disclosure will not be described in detail or will be omitted so as not to obscure the relevant details of the disclosure.

[0064] Various aspects of the novel compositions and methods are described more fully herein with reference to the accompanying drawings. These aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Although some examples and aspects are described herein, many variations and permutations of these examples fall within the scope of the disclosure. Although some benefits and advantages of the various aspects are mentioned, the scope of the disclosure is not intended to be limited to benefits, uses, or objectives. The detailed description and drawings are merely illustrative of the disclosure rather than limiting, the scope of the disclosure being defined by the appended claims and equivalents thereof.

[0065] In this disclosure, “rigid porous carbon agglomerates” means porous carbon agglomerates of primary carbon nanoparticles that resist deformation under high shear mixing, for example, during preparation of a cathode slurry including the rigid porous carbon agglomerates or casting of a slurry including the rigid porous carbon agglomerates to produce one or more layers or films on the cathode substrate. The rigid porous carbon agglomerates resist deformation during shear mixing using a high shear mixer operating at speeds of at least 2000 rpm. Mixing speeds using the high shear mixer may be as high as 20,000 rpm. The rigid porous carbon agglomerates resist deformation at shear rates of at least 500 s’1. The rigid porous carbon agglomerates resist deformation at shear rates of between approximately 200 s’1and 1000 s’1.

[0066] The rigid porous carbon agglomerates may be distinct from commonly known “soft carbons” and “hard carbons. “Soft carbons” are generally carbons which form layers of carbons aligned in stacks as in graphite (or graphitizes) upon heating to high temperatures of at least 1500 °C. “Hard carbons” are carbon that do not graphitize upon heating to high temperatures. The rigid porous carbon agglomerates may be substantially spherical in shape. In some instances, the rigid porous carbon agglomerates may include hard carbons, soft carbons, etched carbons, or any combination thereof, so long as the carbons satisfy the requirement to resist deformation to high shear mixing.

[0067] A primary carbon nanoparticle may be considered as a spheroidal shaped, non- discreet component or building block of an aggregate, separable from the aggregate only by fracturing. A plurality of primary carbon nanoparticles produced by one or more methods including thermal cracking of a hydrocarbon gas, may be coalesced, or joined to form aggregates of primary carbon nanoparticles. A carbon aggregate may be considered as a discrete, colloidal entity that is the smallest dispersible unit, composed of coalesced primarycarbon nanoparticles. The primary carbon nanoparticles may be connected by one or more of van der Waals forces, covalent bonds, ionic bonds, metallic bonds, or by other physical or chemical interactions. “Agglomerates” means “soft agglomerates” or “deformable agglomerates” of primary carbon nanoparticles produced from one or more methods including thermal cracking of a hydrocarbon gas. An example rigid porous carbon agglomerate of primary carbon nanoparticles may be characterized by a principal dimension of at least approximately 1 pm. A plurality of aggregates may be considered as an agglomerate.

[0068] In this disclosure, “graphene” refers to an allotrope of carbon in the form of atomic-scale, hexagonal lattice in which one atom forms each vertex. The carbon atoms in graphene may be sp2hybridized carbon atoms. Additionally, graphene has a Raman spectrum with two main peaks: a G-mode at approximately 1580 cm'1and a D mode at approximately 1350 cm'1(when using a 532 nm excitation laser).

[0069] A lithium- sulfur battery (“Li-S battery”) is notable for its high specific energy. Li-S batteries may replace conventional lithium-ion chemistries (e.g., Li-Co) because of their higher energy density and lower cost, thanks to the wide availability of sulfur, which is the active cathode material in Li-S batteries. Li-S batteries can potentially offer specific energies of approximately 500 W-h / kg, which is significantly better than the specific energy of 150- 250 W-h / kg of conventional Li-ion batteries. Realizing a specific energy of approximately 500 W-h / kg in Li-S batteries may require an electrolyte to sulfur ratio (“E / S ratio”) of less than approximately 5 pL / mgS, and a ratio of the capacities of the anode to cathode (“N / P ratio”) of approximately less than 3. The N / P ratio may be defined as the ratio of respective areal reversible capacity (mAh / cm2) of the negative electrode (anode) and positive electrode (cathode). The N / P ratio in commercial Li-ion batteries is between approximately 1.03 and 1.2.

[0070] Commercialization of Li-S pouch cells has been hampered by limited discharge / charge cycling capabilities of less than approximately 200 cycles. Root cause analysis suggests that Li-anode failure constitutes the main reason for cell failure. During battery cycling, the Li-anode experiences significant volume change caused by repeated stripping (during discharge) and plating (during charge) of lithium. This volume change negatively impacts anode stability, and in particular, the stability of unsupported (hostless) Li-metal anodes. Anode stability is further impacted by an unstable electrode-electrolyte interface and pulverization of the anode caused by cycling because Li has the highestoxidation potential (approximately -3.04V) and can react with almost any electrolyte solution to develop a solid electrolyte interphase (“SEI”).

[0071] The SEI may protect the anode from electrolytes that are thermodynamically reactive. The SEI is electronically insulated, but ionically conductive to Li+ions. As such, the undesirable reactions between Li metal at the anode and the electrolyte may be partially blocked by an SEI. However, the SEI deposited on the anode is generally non-uniform, which results in non-uniform current distribution during plating, and may cause uneven Li deposition and anode crack formation during cycling. Fresh Li metal may be exposed to the electrolyte resulting in the continued consumption of active Li and electrolyte for reformation of SEI.

[0072] Additionally, the localized non-uniform Li deposition and stripping can manifest as dendrites and pits at the anode. Dendrites may cause serious problems to the safety and cyclability of Li metal batteries. Dendrites may be dislodged from the electrode to form ‘dead’ zones of Li. Li dendrites may penetrate through conventional polyolefin separators or even polymer / solid electrolyte separators disposed between the anode and the cathode of a battery, and negatively impact the performance and safety of Li-ion batteries.

[0073] The above problems are further exacerbated in Li-S batteries, which include sulfur confined in a porous carbon cathode as the active cathode material. Sulfur reacts with Li ions forming polysulfides which are soluble in electrolytes. During the discharge cycle, Li ions migrate from the anode to the cathode through the electrolyte where sulfur is reduced to lithium sulfide (Li2S). The sulfur reduction to Li2S is complex and may involve the formation of several intermediate Li polysulfides (Li2Sx, 8 < x < 1). Lithium polysulfides (“Li-PS”) may be formed during the battery discharge cycle as:S8Li2S8Li2S6Li2S4Li2S3^ Li2S2^ Li2S

[0074] Ideally, the Li-PS compounds would oxidize back to sulfur during the charge cycle. In practice, Li-PS compounds leak out from the porous carbon cathode. While sulfur and Li2S are relatively insoluble in most electrolytes, many intermediate polysulfides (“Li- PS”) are soluble and cause irreversible loss of active sulfur from the cathode. The dissolution of Li-PS in the electrolyte requires a large amount of electrolyte (E / S > 3), which reduces battery specific energy. Li-PS compounds diffuse to the anode, where they are reduced to short-chain polysulfides and diffuse back to the cathode where long-chain polysulfides are formed again. At the anode, the polysulfides participate in SEI formation, increase theunevenness of SEI, and aggravate the corrosion of the Li metal anode. This cyclic process commonly known as the “polysulfide shuttle effect” results in the continuous leakage of active material from the cathode, lithium corrosion at the anode, and leads to low coulombic battery efficiency. Further, the conversion of elemental sulfur to Li2Sxsulfur compounds is accompanied by large volumetric expansion at the cathode (which could be as high as 80%), which subjects the cathode to significant mechanical stresses resulting in rapid cathode degradation.

[0075] Additionally, the “shuttle effect” is responsible for self-discharge of Li-S batteries, because of the slow dissolution of Li-PS during battery dormancy. Battery self-discharge reduces battery life and causes safety issues. The repeated volume change and the corrosion reactions at the anode continuously consume active Li and form massive “dead Li,” which may be detached during cycling, leading to poor recyclability of Li-S battery. As previously noted, often the anode contributes to cell failure, either via electrolyte consumption of Li due to corrosion or its depletion during cycling. These challenges limit the commercial viability of high- specific energy Li-S batteries having dense cathodes, limited electrolyte, and limited anode capacity (or low N / P).

[0076] Typical carbonaceous materials used in Li-S batteries are highly non-polar and do not anchor or confine Li-PS compounds in the cathode. Although some level of physical caging of Li-PS compounds may be realized by employing carbonaceous materials of desired pore structure (pore size, pores distribution), Li-PS compounds leak out of the cathode and dissolve in the electrolyte.

[0077] Agglomerates of porous primary carbon nanoparticles including catalyst nanoparticles that chemically bind Li-PS compounds are needed. As previously noted, Li-PS compounds leak out from the porous carbon cathode. While sulfur and Li2S are relatively insoluble in most electrolytes, many intermediate polysulfides (Li-PS) are soluble and cause irreversible loss of active sulfur from the cathode. The catalyst nanoparticles may bind Li-PS intermediate compounds or convert these compounds to Li2S, which is insoluble in the electrolyte.

[0078] Additionally, dense cathodes that can increase the energy density (W-h / L) of Li-S batteries are needed. Dense cathodes are cathodes that have tightly packed agglomerates with a cathode loading of at least 7 mg / cm2based on the total weight of carbonaceous materials, sulfur, binder, and other materials that are typically loaded on a cathode substrate. Sinceagglomerates may be amenable to deforming, rigid and substantially spherical agglomerates that provide for dense packing to maximize ion conductivity and packing density are needed.

[0079] Figure 1A shows a scanning electron microscope (SEM) image 100A of rigid porous carbon agglomerates 141 of porous carbon primary nanoparticles including catalyst nanoparticles 170, according to some implementations. Figure IB shows a schematic diagram 100B of rigid porous carbon agglomerates 141 of porous carbon primary nanoparticles 105 including catalyst nanoparticles 170, according to some implementations. Those skilled in the art will appreciate that the micrographs are shown by way of example only, and that other scales may exist without departing from the scope and spirit of the present implementations. In some implementations, the example rigid porous carbon agglomerates 141 of porous carbon primary nanoparticles 105 may include catalyst nanoparticles 170 dispersed substantially uniformly on one or more of the surfaces of the rigid porous carbon agglomerates 141. In some implementations, the catalyst nanoparticles 170 may also be dispersed within the interconnected porous network 171 disposed between the porous carbon primary nanoparticles 105.

[0080] In some implementations, the catalyst nanoparticles 170 may be dispersed in the pores within the porous carbon primary nanoparticles 105 (pores not shown for simplicity). Example catalyst nanoparticles 170 may include one or more of Mg, MgO, W, WC, or any other metal-based or non-metal-based nanoparticles. The catalyst nanoparticles loading (e.g., the amount of nanoparticles in the rigid porous carbon agglomerate) in the rigid porous carbon agglomerates 141 may be between approximately 10 wt% and approximately 20 wt%, and may be tuned, as desired. In some aspects, the catalyst nanoparticle loading in the rigid porous carbon agglomerates 141 may be between approximately 1 wt% and approximately 50 wt%. In some aspects, the catalyst nanoparticle loading in the rigid porous carbon agglomerates 141 may be between approximately 50 wt% and approximately 90 wt%.

[0081] Figure 2A shows a SEM image 200A of rigid porous carbon agglomerates 241 of porous carbon primary nanoparticles including MgO nanoparticles 270, according to some implementations. Figure 2B shows a cross sectional SEM image 200B of rigid porous carbon agglomerates 241 of porous carbon primary nanoparticles including MgO nanoparticles 270, according to some implementations. As shown in Figure 2A, MgO nanoparticles 270 may be dispersed on the surface of a respective rigid porous carbon agglomerate 241. As shown in Figure 2B, MgO nanoparticles 270 may also be dispersed substantially uniformly within the rigid porous carbon agglomerates 241. MgO nanoparticles 270 may also be dispersed in theinterconnected porous network between the rigid porous carbon agglomerates 241. In some instances, the MgO nanoparticles 270 may be dispersed within the pores of the porous carbon primary nanoparticles (pores not shown for simplicity). In some aspects, there may be an absence of lumping or aggregation of MgO nanoparticles 270 in the rigid porous carbon agglomerate 241, for example, as depicted in Figures 2A-2B.

[0082] As previously noted, agglomerates of porous primary carbon nanoparticles may be dispersed in a solution including one or more polymeric binders and one or more MgO precursors. The agglomerates in solution may be spray dried in a single step at predetermined spray drying conditions and calcined to produce the rigid porous carbon agglomerates 241 including the MgO nanoparticles 270 shown in the examples of Figures 2A-2B. Example MgO precursors may include magnesium acetate. An example binder may include polyacrylonitrile (“PAN”). The average size of the rigid porous agglomerates 241 may be between approximately 100 nm and 500 nm.

[0083] Figures 2C-2D show transmission electron microscopy (TEM) images 200C- 200D of rigid porous carbon agglomerates of porous carbon primary nanoparticles including MgO nanoparticles 270, according to some implementations. In some aspects, the MgO nanoparticles 270 may be supported or encapsulated in 3D graphene layers (3DG) 242. The MgO nanoparticles 270 may be characterized by an average particle size of less than approximately 50 nm. In some implementations, example MgO nanoparticle loadings in the rigid porous carbon agglomerate 241 shown in the examples of Figures 2A-2B may be between approximately 10 wt% and approximately 20 wt%. In some aspects, MgO nanoparticle loading in the rigid porous carbon agglomerates 241 shown in the examples of Figures 2A-2B may be between approximately 1 wt% and approximately 50 wt%. In some aspects, MgO nanoparticle content in the rigid porous carbon agglomerates 241 shown in the examples of Figures 2A-2B may be between approximately 50 wt% and approximately 90 wt%.

[0084] Figure 3A shows a thermogravimetric analysis (TGA) graph 300A of the rigid porous carbon agglomerates 241 of porous carbon primary nanoparticles including MgO nanoparticles 270 shown in the examples of Figures 2A-2B, according to some implementations. As shown in Figure 3 A, the carbon material in the rigid porous carbon agglomerates may be oxidized to CO2 and other gaseous products during TGA analysis in air leaving behind MgO (approximately 10 wt%) in the rigid porous carbon agglomerates. Aspreviously noted, the MgO loading may be tuned by changing the quantity of the metal precursor, for example magnesium acetate, in the solution to be spray dried.

[0085] Figure 3B shows an X-ray diffraction (“XRD”) pattern 300B of rigid porous carbon agglomerates 241 of porous carbon primary nanoparticles including MgO nanoparticles 270 shown in the examples of Figures 2A-2B, according to some implementations. XRD analysis was performed using Cu Karadiation. The XRD pattern exhibits the characteristic fingerprint corresponding to the (111), (200), (220), (311), and (222) planes of polycrystalline cubic structure of MgO nanoparticles (JCPDS No. 45-0946). No other impurity phase was observed. The high intensity of the (200) plane suggests a high degree of crystallinity of the MgO nanoparticles 270. The average crystallite size calculated using the (200) plane was between approximately 21 nm and approximately 22 nm.

[0086] As described below in Example 1 and with reference to Figures 3C-3D, in some implementations, catalyst nanoparticles including MgO dispersed on and within rigid porous carbon agglomerates may bind Li-PS intermediate compounds or convert these compounds to Li2S, which is insoluble in the electrolyte. Without being bound by any particular theory, the resulting reduced concentration of Li-PS compounds in the electrolyte mitigates the “shuttle effect” and increases cycle life of lithium-sulfur batteries. Additionally, cyclic voltammetry tests, described below in Example 2 and with reference to Figure 3E, also demonstrate the mitigation of the “shuttle effect” using MgO nanoparticle catalyst additives dispersed in rigid porous carbon agglomerates disposed in the cathode of lithium- sulfur batteries.

[0087] In some implementations, the example rigid porous carbon agglomerates of porous carbon nanoparticles shown in the examples of Figures 2A-2B may be substantially spherical in shape, which allows for higher packing density of the agglomerates as layers or films on a suitable cathode substrate. In some implementations, the dense cathodes may be characterized by a packing density of at least approximately 7 mg / cm2, which in turn increases the sulfur loading at the cathode and may reduce the N / P ratio in a Li-S battery. Referring also to Figure IB, at any given cathode loading of rigid porous carbon agglomerates, the electrolyte in a Li-S battery may access the interconnected porous network 171 in the agglomerates 141, and subsequently, Li ions in the electrolyte may have improved access to sulfur confined within the agglomerates 141. As previously noted, the catalyst nanoparticles disposed in the interconnected porous network 171 may selectively anchor or cage or chemically bind Li-PS in the Li-S battery cathode. The catalyst nanoparticles may serve as anchor points for chemically binding Li-PS at the cathode.

[0088] In some implementations, the catalyst nanoparticles 170 may include tungsten carbide (“WC”) nanoparticles dispersed substantially uniformly in one or more of the external surfaces of the rigid porous carbon agglomerates 141, the interconnected porous network 171 formed between the rigid porous carbon agglomerates 141, or within the pores of the porous carbon primary nanoparticles 105. The rigid porous carbon agglomerates 141 including tungsten carbide nanoparticles may be produced by dispersing agglomerates in a solution including one or more polymeric binder materials and one or more WC precursors. In some aspects, an example tungsten carbide loading may be between approximately 10 wt% and approximately 20 wt%. In some aspects, an example tungsten carbide loading may be between approximately 1 wt% and approximately 50 wt%. In some aspects, an example tungsten carbide loading may be between approximately 50 wt% and approximately 90 wt%. The average size of the tungsten carbide nanoparticles in the rigid porous carbon agglomerates 141 may be between approximately 100 nm and approximately 300 nm. Precursor chemicals for tungsten carbide nanoparticles may include tungsten disulfide (WS2) or tungsten (VI) oxide (WO3) or ammonium tungstate, or any other suitable precursor. The WC content in the rigid porous carbon agglomerates 141 may be tuned by changing the amount of the metal precursor in the solution to be spray dried.

[0089] Without being bound by any particular theory, the type or choice of the polymeric binder may impact the dispersion of the catalyst nanoparticles and the size of the catalyst nanoparticles in the rigid porous carbon agglomerates. Figure 4A shows a SEM image 400A of example rigid porous carbon agglomerates of porous carbon primary nanoparticles including tungsten carbide (WC) nanoparticles, according to some implementations. Ammonium tungstate was used as the precursor in the solution to be spray dried. PAN was used as a polymeric binder material. The amount of ammonium tungstate was tuned to produce approximately 10 wt% loading of WC in the rigid porous carbon agglomerates. In the example of Figure 4A, tungsten carbide nanoparticles are substantially uniformly dispersed on the surface of the rigid porous carbon agglomerates.

[0090] Figures 4B-4E show SEM-EDS elemental dispersion images 400B-400E, respectively, of rigid porous carbon agglomerates of porous carbon primary nanoparticles including tungsten carbide (WC) nanoparticles, according to some implementations. The elements examined during EDS analysis included carbon (shown in elemental dispersion image 400B), oxygen (shown in elemental dispersion image 400C), sulfur (shown in elemental dispersion image 400D), and tungsten (400E). The example of Figure 4E showssubstantially uniform distribution of tungsten (the elemental mapping of tungsten, M line). Additionally, trace amount of nitrogen was observed (not shown) in the carbonized binder residue resulting from the calcination of the spray dried agglomerates.

[0091] Figure 5A shows a SEM image 500A of rigid porous carbon agglomerates of porous carbon primary nanoparticles including tungsten carbide (WC) nanoparticles, according to some implementations. Ammonium tungstate was used as the precursor in the solution to be spray dried. The amount of ammonium tungstate was tuned to produce approximately 10 wt% loading of WC in the rigid porous carbon agglomerates. PMMA was used as the polymeric binder material. As shown in Figure 5A, tungsten carbide particles are formed, dispersed, or otherwise disposed on the surface of the rigid porous carbon agglomerates. In contrast to the rigid porous carbon agglomerates obtained using PAN as the binder material, the tungsten carbide particles on rigid porous carbon agglomerates obtained using PMMA as the binder material are larger in size and less uniformly dispersed; that is, localized lumps of WC particles may be seen in Figure 5A.

[0092] Figures 5B-5E show SEM-EDS elemental dispersion images 500B-500E, respectively, of rigid porous carbon agglomerates of porous carbon primary nanoparticles including tungsten carbide (WC) nanoparticles, according to some implementations. The elements examined during EDS analysis included carbon (shown in elemental dispersion image 500B), oxygen (shown in elemental dispersion image 500C), sulfur (shown in elemental dispersion image 500D), and tungsten (shown in elemental dispersion image 500E). As shown in Figure 5E, the elemental mapping of tungsten shows localization and variations in the distribution of tungsten as observed with the PAN binder material. In contrast to rigid carbon agglomerates obtained using PAN as the binder material, trace amounts of nitrogen was not observed in the carbonized residue resulting from the calcination of the spray dried agglomerates.

[0093] Figure 6A shows a SEM image 600A of rigid porous carbon agglomerates of porous carbon primary nanoparticles including tungsten carbide (WC) nanoparticles, according to some implementations. Ammonium tungstate was used as the precursor in the solution to be spray dried. The amount of ammonium tungstate was tuned to produce approximately 10 wt% loading of WC in the rigid porous carbon agglomerates. PEI-800 was used as the polymeric binder material. In the example of Figure 6A, tungsten carbide nanoparticles are uniformly dispersed on the surface of the rigid porous agglomerates. Theaverage size of the WC nanoparticles may be smaller than that obtained using PAN as the binder material.

[0094] Figures 6B-6E show SEM-EDS elemental dispersion images 600B-600E, respectively, of rigid porous carbon agglomerates of porous carbon primary nanoparticles including tungsten carbide (WC) nanoparticles, according to some implementations. The elements examined during EDS analysis included carbon (shown in elemental dispersion image 600B), oxygen (shown in elemental dispersion image 600C), sulfur (shown in elemental dispersion image 600D), and tungsten (shown in elemental dispersion image 600E). Figure 6E shows substantially uniform distribution of tungsten (the elemental mapping of tungsten, M line). As seen with the rigid carbon agglomerates obtained using PAN as the binder material, trace amount of nitrogen was observed in the carbonized binder residue resulting from the calcination of the spray dried agglomerates.

[0095] Figure 7A shows an example X-ray diffraction (XRD) pattern 700A of rigid porous carbon agglomerates of porous carbon primary nanoparticles including WC nanoparticles, according to some implementations. PAN was used as the binder material and WO3 as the tungsten carbide precursor. The XRD pattern confirmed the presence of WC and W2C with WC being in crystalline form. The WC crystallite size based on the (100) plane was approximately 25.2 nm. The XRD pattern exhibits the characteristic fingerprint corresponding to the (001), (100), (101), (110), and (002) planes of tungsten carbide nanoparticles.

[0096] Accordingly, in some implementations, the particle size and dispersion of the catalyst nanoparticles in rigid porous carbon agglomerates produced using the example method of 1000A (described below with reference to Figure 10A) may be tuned by the choice of the binder material. In some instances, and referring to Figures 4A-4E, with PAN as the binder in operation 1000A for producing rigid porous carbon agglomerates including dispersed tungsten carbide (WC) nanoparticles, the tungsten carbide nanoparticles may be substantially uniformly dispersed on the surface of the rigid porous carbon agglomerates. In some other instances, and referring to Figures 5A-5E, with PMMA as the binder in operation 1000A, the tungsten carbide particles may be relatively larger in size and less uniformly dispersed; that is, localized lumps of WC particles may be observed on the rigid porous carbon agglomerates. In some other aspects, and referring to Figures 6A-6E, with PEI as the binder in operation 1000 A, the tungsten carbide particles may be relatively smaller in size(relative to the particle size of tungsten carbide formed using PAN as the binder) and may also be uniformly dispersed in the rigid porous carbon agglomerates.

[0097] In some implementations, in addition to the size of the catalyst nanoparticles and the dispersion of the catalyst nanoparticles on the surface of the rigid porous carbon agglomerates, the electrochemical performance of lithium-sulfur cells with cathode porous carbon agglomerates including catalyst nanoparticles may also be dependent on the surface area and porosity of the rigid porous carbon agglomerates. Due to the porous structure of the rigid porous carbon agglomerates, catalyst nanoparticles may also be dispersed within the rigid porous carbon agglomerates. As such, particle size and dispersion of the catalyst nanoparticles within the rigid porous carbon agglomerates may also impact electrochemical performance. Additional details are described below with reference to Example 3 and Figure 7B.

[0098] In some implementations, an example lithium-sulfur battery cathode may include one or more porous carbon layers including rigid porous carbon agglomerates of porous carbon primary nanoparticles. A respective porous carbon primary nanoparticle may include an inner porous shell disposed about a center of the respective porous carbon primary nanoparticle and enclosing an inner porous carbon region, an outer porous shell enclosing an outer porous carbon region disposed between the inner shell and the outer shell, and an interconnected porous network disposed in and in fluid communication with the inner and outer porous carbon regions. Figure 8A shows a schematic diagram 800A of an example porous carbon primary nanoparticle 805, according to some implementations. In some aspects, the porous primary carbon nanoparticle 805 may resemble carbon nano-onions (CNOs). As shown in the example of Figure 8 A, the porous primary carbon nanoparticle 805 may include a core (inner) porous carbon region 811 defined by a first porosity and enclosed within an inner porous shell 813. The inner porous carbon region 811, which may also be referred to herein as the first porosity region, may include a plurality of first pores 801 dispersed therein. An outer porous carbon region 812, which may also be referred to herein as the second porosity region, may be disposed between the inner porous shell 813 and an outer porous shell 810 and may include a plurality of second pores 802 dispersed therein. The inner porous carbon region 811 and the outer porous carbon region 812 may be interconnected by one or more of the first pores 801 or one or more of the second pores 802, thereby interconnecting the first and second porosity regions. That is, the inner porous carbon region 811 may be configured to be in fluid communication with the outer porouscarbon region 812 through an interconnected porous network. The inner porous carbon region 811 may be defined by a first pore density, and the outer porous carbon region 812 may be defined by a second pore density that is similar to, or different than, the first pore density.

[0099] Example porous primary carbon nanoparticle 805 may be characterized by an average size or principal dimension (diameter, length, width) of less than approximately 200 nm. In some implementations, an average pore size may gradually decrease along a radial direction from the center 816 of the nanoparticle 805 to the outer boundary 813 of the nanoparticle 805. In some implementations, porous primary carbon nanoparticle 805 may be characterized by a range of pore sizes and pore distributions in each region. The first pores 801 may be configured to retain poly sulfides 820, and the second pores 802 may provide pathways or channels for the transport of lithium ions (not shown for simplicity) into and from the porous primary carbon nanoparticles 805 and for pre-loading sulfur 824 into the nanoparticles.

[0100] Figure 8B shows a transmission electron microscopy (“TEM”) image 800B of aggregates 840 of porous primary nanoparticles 805, according to some implementations. Example carbon aggregates 840 may include an interconnected porous network disposed between adjacent carbon nanoparticles 805. Aggregate 840 may include a plurality of porous carbon primary nanoparticles 805 and, in some instances, may resemble a “string-of-pearls.” In some implementations, the size or principal dimension of aggregate 840 may be between approximately 50 nm and 500 nm.

[0101] Figure 8C shows a TEM image 800C of agglomerates 845 of porous primary carbon nanoparticles 805, according to some implementations. An agglomerate 845 of porous carbon primary nanoparticles 805 may be characterized by a surface area of less than approximately 3000 m2 / g. In some implementations, an example agglomerate 845 may be spherical in shape. In some implementations, an agglomerate 845 may be of any shape, including one or more of spherical, spheroidal, dumbbell, cylindrical, elongated cylindrical type, rectangular prism, disk, wire, or irregular.

[0102] Figure 8D shows a TEM image 800D of surface etched agglomerates 842 of porous primary carbon nanoparticles, according to some implementations. Example agglomerates 845 may be surface etched using methods that include CO2 etching to create pores on the external surface of the agglomerates 845 and to increase the surface area of the carbon agglomerates 845 to yield surface etched agglomerates 842. After etching, the surfaceetched agglomerates 842 may include three-dimensional graphene carbons (“3DG carbons”) including graphene layers interconnected as three-dimensional (“3D”) graphene structures (not shown for simplicity). The surface etched agglomerates 842 of porous primary carbon nanoparticles may be characterized by a Raman spectroscopy signature with an ID / IG ratio of approximately between 0.95 and 1.05. As previously noted, the surface etched agglomerates 842 may be assembled as rigid porous carbon agglomerates by processes including spray drying. In some other implementations, the rigid porous carbon agglomerates may be characterized by an electrical conductivity of between approximately 500 S / m and approximately 20,000 S / m when compressed at a pressure of approximately 12,000 pounds per square inch (psi).

[0103] Figure 9 shows a schematic diagram 900 of another example porous primary carbon nanoparticle 905, according to some implementations. Example tri-zone porous primary nanoparticle 905 may include a first core (inner) carbon zone or region 951, nested within a second intermediate carbon zone or region 952, which in turn is nested within a third outer carbon zone or region 953. Example first zone 951 may include pores 961 having an average size or principal dimension (diameter, length width) of less than approximately 40 nm, the second zone 952 may include pores 962 having an average size or principal dimension of less than approximately 35 nm, and the third zone 953 may include pores 963 having an average size or principal dimension of less than approximately 30 nm. In some example implementations, pores 961 may be characterized as macropores, the pores 962 in the intermediate region 952 may be characterized as mesopores, and the pores 963 in the outer region 952 as micropores.

[0104] In some implementations, the principal dimension DI of first zone 951 may be less than approximately 100 nm, D2 may be less than approximately 150 nm, and the third zone 953 may have a principal dimension D3 of approximately 200 nm. The relative dimensions, porosities, and electrical conductivities of the first zone 951, the second zone 952, and the third zone 953 may be tuned to achieve a desired balance between minimizing the polysulfide shuttle effect and maximizing the specific capacity of a host battery. The first zone (inner core zone) 951 may have a density of carbons of less than approximately 1 g / cc. The outer zone 953 bounded by the perimeter of the particle 905 or outer shell 955 may have a density of carbons of between approximately less than 1 g / cc and 3.5 g / cc. The intermediate zone 952 may have a density of carbons of between approximately 0.5 g / cc and 3 g / cc. Each porous carbon region 951, 952, and 953 may be characterized by an averagepore size and an average pore density associated with each region. The average pore size associated with each of regions 951-953 may decrease along a radial direction from the center of the porous primary carbon nanoparticle 905 to the outer porous shell 955.

[0105] Agglomerates of porous primary carbon nanoparticles 905 may be surface etched using methods that include CO2 etching to create pores on the external surface of the agglomerates and to increase the surface area of the carbon agglomerates. After etching, the agglomerates may include three-dimensional graphene carbons (“3DG carbons”) including graphene layers interconnected as three-dimensional (“3D”) graphene structures. The resulting surface etched agglomerates of porous primary carbon nanoparticles 905 may be characterized by a Raman spectroscopy signature with an ID / IG ratio of approximately between 0.95 and 1.05.

[0106] In some implementations, the resulting agglomerates may be produced by thermal cracking of hydrocarbon feedstock as disclosed in commonly-owned U.S. Pat. No. 9,862,602, U.S. Pat. No. 10,112,837, U.S. Pat. No. 11,053,121, and / or U.S. Pat. Pub. No. 2021 / 0292170, all of which are incorporated by reference herein in each of their entireties.

[0107] Figure 10A shows an illustrative flowchart 1000A depicting an example single- step operation for producing a lithium-sulfur battery cathode including rigid porous carbon agglomerates, according to some implementations. In some instances, operation 1000A may begin at 1002 with providing agglomerates of primary carbon nanoparticles. Any one of the previously described agglomerates may be used at 1002. Example primary carbon nanoparticles may include particles 805 or 905, as previously disclosed. The porous carbon agglomerates may include carbon nano-onions (“CNOs”) and other carbon allotropes. The porous carbon agglomerates may include two or more interconnected multi-walled spherical fullerenes (“MWSFs”). The porous carbon agglomerates may include one or more of fewlayer graphene (“FLG”) interconnected platelets, multi-layer graphene (“MLG”) interconnected platelets, graphite, flat graphene, or wrinkled graphene.

[0108] In some instances, the agglomerates may be surface etched at 1002 using methods that include CO2 etching to create pores on the external surface of the agglomerates and to increase the surface area of the carbon agglomerates. Surface etching methods may include one or more of steam etching, or etching using KOH, ZnCh or HNO3. At 1004, operation 1000A continues with producing a solution including one or more catalyst precursors soluble in a spray-drying solvent. Example solvents may include dimethyl formamide (“DMF”). Catalyst precursors may serve as a source for the catalyst (metal or non-metal based)nanoparticles. The composition of the solution may be tuned based on one or more of the desired catalyst nanoparticles loading in the carbon agglomerates, pore structure of the carbon agglomerates, and the like.

[0109] In some implementations of operation 1000A, the one or more catalyst precursors may include one or more of acetate, oxalate, sulfide, or nitrides salts of metals. For example, magnesium acetate, indium triacetate, niobium (V) oxalate, ammonium tungstate, tungsten disulfide or tungsten (VI) oxide, or combination thereof, may be used as catalyst precursors. The amount of catalyst precursors may be between approximately 5 wt% and approximately 25 wt% of weight of the agglomerates provided at 1002.

[0110] At 1006, operation 1000A continues with dispersing the agglomerates provided at 1002 in the solution including the catalyst precursor. The solution may be sonicated for a predetermined time. At 1008, operation 1000A continues with adding one or more polymeric binders in a suitable solvent (e.g., DMF) to the solution comprising dispersed carbon agglomerates and catalyst precursors. In some instances, a suitable binder material such as polyacrylonitrile (“PAN”) may be used. The amount of polymeric binder may be between approximately 5 wt% and 20 wt% of the weight of the agglomerates. The amount of polymeric binder may be approximately 10 wt% of the weight of the agglomerates.Alternately, steps 1004, 1006, and 1008 may be combined into a single step for producing a solution of catalyst precursors including polymeric binders and dispersed agglomerates of porous carbon primary nanoparticles.

[0111] At 1012, operation 1000A may continue with spray drying the agglomerates dispersed in the solution at 1008 using a suitable spray dryer. For example, a spray dryer supplied by BUCHI (Delaware) may be used. At 1014, operation 1000A may continue with calcining the spray dried agglomerates at between approximately 800 °C and approximately 1200°C in the presence of argon, or a gas mixture of compressed dry air and one or more of argon or nitrogen, or an argon and hydrogen gas mixture. The product of step 1014 may include rigid porous carbon agglomerates including substantially uniformly dispersed catalyst nanoparticles and carbonized binder residue, as previously disclosed.

[0112] As previously noted, the type or choice of the polymeric binder may impact the dispersion of the catalyst nanoparticles and the size of the catalyst nanoparticles in the rigid porous carbon agglomerates. Carbonized residue of the example polymeric binder materials may be dispersed in the rigid porous carbon agglomerates to provide mechanical strength to the carbon layers or films at the Li-S battery cathode.

[0113] In some implementations, example polymeric binders may include one or more of styrene butadiene rubber, vinyl polymers, polyvinylidene fluoride, poly acrylic acid (“PAA”), carboxyl methyl cellulose, polyvinylpyrrolidone, polyvinyl acetate, polyacrylonitrile (“PAN”), polyethyleneimine (“PEI”), polymethylmethacrylate (“PMMA”), pitch, formaldehyde-based resins, or any combination thereof. Some binders such as PAN and PEI- 800 may be carbonized to binder residue, which may include trace levels of nitrogen. Other binders such as PMMA may completely burn-off while leaving behind no residue.

[0114] An example precursor for MgO nanoparticles in rigid porous carbon agglomerates may include magnesium acetate. PAN or PEI may be used as the polymeric binder. An example precursor for WC may include tungsten (VI) oxide (WO3), ammonium tungstate, or tungsten disulfide (WS2). PAN or PEI may be used as the binder. The type of precursor salt or chemical may also impact the particle size of MgO or WC after the calcining step. For example, the average particle size of WC may be between approximately 200 nm and 1 pm with WS2 as the precursor. The average particle size of WC may be between approximately 100 nm and 300 nm with WO3 as the precursor. The average particle size and size distribution of the metal-based nanoparticles may be tuned by selecting one or more of catalyst precursor type, binder type, or calcining protocols that include temperature, ramp rate, hold time and gas atmosphere.

[0115] At 1016, operation 1000A may continue with producing carbon-sulfur composites (“CSC”) by sulfurizing the rigid porous carbon agglomerates produced at 1014. The sulfur to carbon weight ratio may be between approximately 1:5 and 10:1. The sulfur to carbon weight ratio may be approximately 3. At 1018, operation 1000A may continue with casting a slurry including the carbon-sulfur composites as one or more layers or films of carbon material on a suitable substrate to form the cathode in an example Li-S battery. The cathode substrate may include a cathode current collector. The cathode current collector may include aluminum. As previously noted, the rigid porous carbon agglomerates resist deformation under high shear mixing, and therefore produce films or layers of carbon of desired porosity, thickness, and packing density. The rigid porous carbon agglomerates may also enable the casting of carbons films with desired density gradients. The packing density of the carbons including the example rigid porous carbon agglomerates having dispersed catalyst nanoparticles may be at least approximately 7 mg / cm2when disposed as films or layers on a suitable cathode substrate.- l-

[0116] The rigid porous carbon agglomerates produced in step 1014 may be spherical in shape. The Raman spectroscopy signature of the rigid porous carbon agglomerates may be characterized by an ID / IG ratio of between approximately 0.95 and approximately 1.05. The average size of the rigid porous carbon agglomerates of 3DG carbons may be at least approximately 1 pm. In some instances, the rigid porous carbon agglomerates may be subjected to etching such as CO2 etching to create pores on the external surface of the agglomerates and to increase the surface area of the agglomerates.

[0117] In some implementations, rigid porous carbon agglomerates may be formed using alternate methods to spraying drying of surface etched agglomerates. In some implementations, an example process may include producing a slurry or mixture of agglomerates with a binder resin and carbonizing the slurry at a temperature of at least 500 °C. In some implementations, a formaldehyde -based resin may be used to produce the agglomerate -resin slurry. The resulting rigid porous carbon agglomerates may be in the form of carbon-based pellets and may be milled down to desired size. In some other implementations, an example process may include producing a slurry or dispersion of agglomerates in water and evaporating water to form carbon-based pellets. The resulting rigid porous carbon agglomerates may be in the form of carbon-based pellets and may be milled down to desired size. Etching is not a prerequisite for forming rigid porous carbon agglomerates. Rigid porous carbon agglomerates may be produced using unetched carbon agglomerates. Additionally, catalyst nanoparticles precursors may be added to the agglomerate -resin slurry, or the agglomerate-water dispersed slurry and calcined to produce rigid porous carbon agglomerates that include catalyst nanoparticles. Other methods for incorporating catalyst nanoparticles in agglomerates such as electrospinning, hydrothermal or freeze-drying followed by a pyrolysis process are not scalable, employ harsh chemicals, and are not desirable.

[0118] The example CSC including rigid porous carbon agglomerates including catalyst nanoparticles as disclosed above may be subject to one or more surface treatments to improve Li ion or electron conductivity. Figure 10B shows schematic diagrams 1025 and 1027 of hard porous carbon agglomerates including ion and / or electron conducting surface coating, according to some implementations. CSC 1025 of rigid porous carbon agglomerates having catalyst nanoparticles may be coated with Li-ion conducting or electron conducting surface coatings using spray drying or any other suitable coating operation. The surface coating may be disposed on the surface of each agglomerate to improve ionic conductivity or electronicconductivity of the agglomerates when they are disposed as one or more layers on a cathode substrate. Surface coating 1029 may include films of one or more of lithium lanthanum zirconium oxide (“LLZO”), lithium 3-glycidyloxypropanesulfonate (“LiGPS”), lithium phosphorus oxynitride (“LiPON”), or lithium bis(trifluoromethanesulfonyl)imide (“LiTFSI”), or combinations thereof. The surface coating or film 1029 may be configured to be an integral part of the structure of each agglomerate resulting in increased contact between agglomerates, which increases Li-ion conductivity or electron conductivity even with rigid porous carbon agglomerates. As such, Li-ion conducting additives such as lithium salts may not be added into the cathode slurry or to the binders used in typical Li-S cathode slurries.

[0119] In some implementations, the CSC 1027 including rigid porous carbon agglomerates including catalyst nanoparticles and an electron or Li-ion conducting surface coating may be assembled in layers on a cathode substrate with high packing density, but also maintaining clear void spaces between the agglomerates to allow for high mobility in the Li- ions in the battery electrolyte. The natural voids between the rigid porous carbon agglomerates may allow for the Li-S battery electrolyte including Li-ions to freely access active sulfur confined in the rigid porous carbon agglomerates.

[0120] Figure 10C shows an illustrative flowchart 1000C depicting another example operation for producing a lithium-sulfur battery cathode including hard porous carbon agglomerates, according to some implementations. In some instances, operation 1000C may begin at 1020 with providing CSC 1025 including rigid porous carbon agglomerates including catalyst nanoparticles, as previously disclosed herein. At 1022, operation 1000C may continue with dispersing CSC in a solution including one or more Li-ion conducting or electron conducting salts. At 1024, operation 1000C may continue with spray drying the solution of ion conducting or electron conducting salts including dispersed CSC to produce CSC having an ion conducting or electron conducting film 1027 or surface coating on each agglomerate. The CSC ion conducting or electron conducting film may be dried. At step 1026, operation 1000C may continue with casting a slurry including the carbon-sulfur composites having the surface coating as one or more layers or films of carbon material on a suitable cathode substrate to form the cathode in an example Li-S battery. The cathode substrate may include a cathode current collector such as aluminum.

[0121] In some implementations, after casting the slurry to form one or more layers including rigid porous carbon agglomerates on a cathode substrate at 1018 in method 1000A (as illustrated in Figure 10A) or at 1026 in method 1000C (as illustrated in Figure 10C), theoperation of fabricating a lithium- sulfur battery cathode may continue with drying and calendering the one or more layers to densify the cathode layers. Increasing the density of the cathode layers by calendering may improve the adhesion of the one or more cathode layers to the cathode substrate. Figure 10D shows a plot WOOD illustrating an increase in adhesion of the cathode layers to the cathode substrate as a function of cathode layer density, according to some implementations. As can be seen, as cathode layer density increases from approximately 0.45 g / cc to approximately 1 g / cc, cathode layer adhesion increases almost linearly from approximately 0.3N to approximately 2N. Increasing adhesion of the cathode layers may prevent cracking and / or delamination of the cathode layers. However, a dense cathode layer suggests a reduction in the porosity of the cathode layers and, as such, a reduction in the wettability of the cathode layer by the liquid electrolyte. Accordingly, increasing the density of the cathode layers may result in a decrease in electrochemical performance of lithium-sulfur cells.

[0122] In some implementations, and without being bound by any particular theory, cathode layers including rigid porous carbon agglomerates including any one of the previously described nanoparticle catalyst additives (for example, MgO, tungsten carbide, and similar examples) may offset the loss in electrochemical performance due to calendering of the cathode. That is, in some implementations, electrochemical performance and mechanical stability of the one or more cathode layers may be improved by incorporating nanoparticle catalyst additives in the one or more cathode layers. Additional details are provided below with reference to Example 7 and Figure 17.

[0123] In some implementations, as described below with reference to Figures 11A-11B, an example cathode for a lithium-sulfur battery may include rigid porous carbon agglomerates of porous carbon primary nanoparticles, which include one or more interconnected bundles of electrically conductive graphene layers. In some aspects, the graphene layers may be arranged as one or more stacks connected to each other and defining a 3D porous scaffold structure including mesopores. In some other aspects, the one or more stacks may be disposed substantially orthogonal to each other. In some instances, the graphene layers may be characterized by a linear dimension of between approximately 50 nm and 200 nm. In some other instances, the graphene layers may include one or more of single layer graphene (“SLG”), few layer graphene (“FLG”), or many layer graphene (“MLG”).

[0124] Figure 11 A shows a schematic diagram of a mesoporous carbon nanoparticle1100A having an interconnected bundle of electrically conductive graphene layers arrangedto form a 3D open porous scaffold structure, according to some implementations. Nanoparticle 1100A and porous carbon agglomerates including nanoparticles 1100A may be produced using a high throughput, low-cost, cracking of a hydrocarbon gas such as natural gas, in an atmospheric microwave plasma reactor. An example microwave plasma reactor is disclosed in commonly-owned U.S. Pat. No. 9,767,992, which is incorporated by reference herein in its entirety. For example, the agglomerates may be formed in-flight and grown by adding additional carbon-based materials derived from incoming carbon-containing gas within a microwave-plasma reaction chamber.

[0125] The carbon nanoparticles 1100A may include three-dimensional (“3D”) multimodal mesoporous carbon nanoparticles. A mesoporous material, as generally understood and as referred to herein, includes a material containing pores with diameters between 2 nm and 50 nm, according to IUPAC nomenclature. For the purposes of comparison, IUPAC defines microporous material as a material having pores smaller than 2 nm in diameter and defines macroporous material as a material having pores larger than 50 nm in diameter. In some instances, mesoporous carbon particle 1100A may be characterized by a three- dimensional (“3D”) hierarchical porous structure including pores 1180. In some aspects, at least a portion of the hierarchical porous structure may further define a 3D open porous scaffold structure 1181.

[0126] The nanoparticle 1100A may include one or more interconnected bundles 1182 of electrically conductive graphene layers or sheets. Each interconnected bundle 1182 may include one or more stacks 1183 of graphene layers. Each stack 1183 may include a plurality of graphene layers 1186 that are generally stacked horizontally as more clearly shown in stack 1184. One or more stacks 1183 of graphene layers 1186 may be arranged to form a 3D porous scaffold structure 1181 including mesopores. That is, a plurality of stacks 1183 of electrically conductive graphene layers 1186 may be sintered together to define the 3D open porous scaffold structure 1181 (which includes mesopores 1180 in the example of Figure 11A). In some implementations, one or more of the stacks 1183 may be connected substantially orthogonal to each other. The open porous scaffold structure 1181 may be configured to provide electrical conduction between contact points (not shown for simplicity) of the stacks of graphene layers 1186. In some implementations, each graphene layer 1186 may be characterized by a diameter or linear dimension (“La”) of between approximately 50 nm to approximately 200 nm. In some implementations, the graphene stack 1183 may include few layer graphene (“FLG”), which may be composed of 5 to 15 layers of graphene.

[0127] A plurality of porous carbon primary nanoparticles 1100A may be coalesced or joined to form porous carbon agglomerates of porous carbon primary nanoparticles. In this disclosure, three-dimensional graphene carbons (“3DG carbons”) include porous carbon agglomerates of mesoporous nanoparticles 1100A. In some implementations, the example 3DG carbons described herein may be characterized by a Brunauer-Emmett-Teller (“BET”) surface area measured using nitrogen gas of approximately 50 to 300 m2 / g. In some implementations, the 3DG carbons may be characterized by a graphene to amorphous carbon ratio of between approximately 1% and 95%. In some implementations, the 3DG carbons may be characterized by a carbon purity of at least 99.9%. The 3DG carbons may be characterized by an electrical conductivity of between approximately 500 S / m and approximately 20,000 S / m when compressed at pressure of approximately 12,000 pounds per square inch (“psi”). The open porous scaffold structure 1181, while confining sulfur, may also provide a host scaffold-type structure to manage volume expansion due to the formation of long chain poly sulfides.

[0128] In some implementations, sulfur may be confined in the pores 1180 of open porous scaffold structure 1181. In some implementations, sulfur may also be confined in the scaffold structure spaces 1185 formed by orthogonally joined stacks 1183 of graphene layers 1184.

[0129] The porous carbon agglomerates described herein and characterized using Raman spectroscopy show a high degree of order and uniformity of structure. In this disclosure, “graphene” refers to an allotrope of carbon in the form of a two-dimensional, atomic-scale, hexagonal lattice in which one atom forms each vertex. The carbon atoms in graphene may be sp2hybridized carbon atoms. Additionally, graphene has a Raman spectrum with two main peaks: a G-mode at approximately 1580 cm'1and a D mode at approximately 1350 cm'1(when using a 532 nm excitation laser). The porous carbon agglomerates may be characterized by a Raman spectroscopy signature having an ID / IG ratio between approximately 0.95 and approximately 1.05.

[0130] In some implementations, the agglomerates 1100A may include a plurality of interconnected crinkled 3D graphene sheets, a plurality of non-hollow carbonaceous spherical particles (“NHCS”), flat graphene, wrinkled graphene, or a plurality of carbon nano-onions (“CNOs”). In some implementations, the agglomerates may include wavy or flexible graphene platelets that resemble crinkled paper and may be produced using microwaveprocesses. The graphene platelets may be flexible as they may be fused with each other at sp3type defects in a sp2graphene lattice structure.

[0131] Figure 1 IB shows a SEM micrograph 1100B of agglomerates 1102 of porous carbon primary nanoparticles, according to some implementations. In some implementations, plasma-based processing conditions, e.g., as applied or performed in a reactor such as a microwave reactor, may be adjusted with a high degree of tunability to achieve graphene-on- graphene densification to yield the agglomerate 1102. Agglomerate 1102 may be surface etched using methods including CO2 etching to create pores on the external surface of the agglomerates and to increase the surface area of the agglomerates.

[0132] In some implementations, the agglomerates 1100B may be treated to form rigid porous agglomerates including catalyst nanoparticles, using any of the methods as previously described herein. The rigid porous agglomerates including catalyst nanoparticles may be sulfurized to form carbon-sulfur composites. (“CSC”). A slurry including the carbon-sulfur composites may be cast as one or more layers or films of carbon material on a suitable substrate to form the cathode in an example Li-S battery. The cathode substrate may include a cathode current collector such as aluminum. As previously described, the rigid porous carbon agglomerates are resistant to deformation under high shear mixing and therefore produce films or layers of carbon of desired porosity and thickness. The agglomerates may be characterized using Raman spectroscopy and show a high degree of order. The agglomerates 1000B may be characterized by a Raman spectroscopy signature having an ID / IG ratio between approximately 0.95 and approximately 1.05.

[0133] Any one of the Li-S battery cathode implementations previously described herein may be configured or disposed for use in cylindrical batteries, prismatic batteries, pouch cells, or any other suitable geometrical shape. A Li-S cylindrical battery may comport with the dimensions of an 18650 battery (approximately 18 mm diameter x approximately 65 mm length), a 21700 (approximately 21 mm diameter x approximately 70 mm length) battery or a 4680 (approximately 46 mm diameter x approximately 80 mm length) battery. In some implementations, a Li-S battery may have a prismatic form factor that can comport with the dimensions of a CP3553 battery. Lor example, an example Li-S battery may have a height between approximately 56 mm and approximately 58 mm, a length between approximately 34 mm and approximately 36 mm, and a width between approximately 6 mm and approximately 8 mm.

[0134] Figure 12 shows a schematic diagram 1200 depicting an example cylindrical battery 1500, according to some implementations. Battery 1200 may include a shell 1210 and a jelly roll 1220. Shell 1210 may have a longitude axis indicated as AA’ in Figure 12, and jelly roll 1220 may be disposed along the longitudinal axis within shell 1210. Jelly roll 1220 may have a cross section in a circle, a rectangle, a square, a triangle, or any other geometric shapes. Jelly roll 1220 may include an anode 1222, a first barrier layer (or separator layer) 1224, a cathode 1226, and a second barrier layer 1228, each in the form of a rollable sheet. Anode 1222, first barrier layer 1224, cathode 1226, and the second barrier layer 1228 may be laminated on top of one another. As such, anode 1222 and cathode 1226 may be separated by the first and the second barrier layers to avoid undesirable short circuiting within battery 1200. In some other implementations, a center pin or mandrel (not shown in Figure 12 for simplicity) may be attached to an inner edge of anode 1222, and the lamination of cathode-first barrier layer-anode-second barrier layer may be radially wound or rolled around the center pin to form the jelly roll 1220. Anode current collector 1202 (in the event the anode is not a free-standing anode) and cathode current collectors 1204 may be integrated into the anode and cathode layers, respectively.

[0135] In some implementations, anode 1222, first barrier layer 1224, cathode 1226, and second barrier layer 1228 may share the same dimensions, and the sheets may be aligned with one another during the rolling process so that there are no sheets protruding from the jelly roll 1220. Either anode 1222 or cathode 1226 current collectors may include a current collector tab, which may protrude out after the sheets are wounded into the jelly roll 1220. Tab 1223 may connect the anode 1222 or the cathode 1226 to a negative or positive terminal (not shown in Figure 12 for simplicity), respectively, via any suitable process including a mechanical welding process. In some implementations, tab 1223 may be the cathode current collector tab. The anode current collector 1202 may be disposed at the outer edge of the jelly roll, and the cathode current collector tab 1223 may be disposed approximately in the center of the jelly roll.

[0136] In some implementations, the electrode sheet, either the anode 1222 or the cathode 1226, may be arranged in a misalignment with the other electrode sheet and the first and the second barrier layer during the rolling process so that a portion 1225 may protrude out of the jelly roll 1220. In some aspects, an electron conductive glue (not shown in Figure 12 for simplicity) may be disposed within shell 1210 at the top and bottom of shell 1210. The protruding portion 1225 may be connected to the negative or positive terminal of shell 1210via electron conductive glue, and thereby eliminates the need for a mechanical welding process. In some implementations anode 1222, anode current collector (not shown), first barrier layer 1224, cathode 1226, cathode current collector (not shown) and the second barrier layer 1228 may be laminated on top of one another. A center pin or mandrel (not shown in Figure 12 for simplicity) may be configured as the cathode terminal and may be attached to the cathode current collector. When disposed as a jelly roll, the anode current collector 1202 may be disposed at the outer edge of the jelly roll, and the cathode current collector 1204 may be disposed approximately in the center of the jelly roll.

[0137] In various implementations, anode 1222 may be any suitable material that is typically used as an anode in a Li-S battery. For example, anode 1222 may be a lithium foil or a lithium substrate. Anode 1222 may include a current collector to support the lithium foil or the lithium substrate. In some implementations, the anode 1222 may include free-standing Li-alloy anodes.

[0138] In some implementations, cathode 1226 may include one or more layers of films or CSC including any of the previously described rigid porous carbon agglomerates including metal nanoparticles. Cathode 1226 may be disposed on cathode current collector 1204. The cathode films may coat both sides of a current collector (not shown in Figure 12 for simplicity), such as an aluminum foil, to provide the maximum cathode capacity. The cathode CSC including any of the previously described rigid porous carbon agglomerates having metal nanoparticles may include multiple pores to micro-confine sulfur as the cathode electroactive material. The electroactive material (sulfur) may constitute approximately between 60 wt% and 90 wt% of the cathode films. The electroactive material of the cathode may include other suitable sulfur-containing materials, such as lithium sulfide.

[0139] Battery 1200 may have an electrolyte (not shown in Figure 12 for simplicity) incorporated into the jelly roll 1220. In some implementations, battery 1200 may have a liquid electrolyte that may be added to shell 1210 after jelly roll 1220 is disposed in shell or casing 1210. In some other implementations, battery 1200 may include a non-aqueous electrolyte such as solid-state electrolyte, gel electrolyte, or polymer film electrolyte incorporated into jelly roll 1220. For example, between the first and the second barrier layers 1224 and 1228, one barrier layer may function as a separator and the other one may function as a non-aqueous electrolyte film. In some other implementations, each of the first and second barrier layers 1224 and 1228 may function as both a separator and a non-aqueous electrolyte film. An example fluorinated ether electrolyte may include 50:25:25 (vol%) of1,2-dimethoxyethane (“DME”) : 1,3-dioxolane (“DOL”) : bis (2,2,2-trifluoroethyl) ether (“BTFE”) with approximately 0.4 M lithium bis (trifluoromethanesulfonyl) imide (“LiTFSI”) and approximately 2 wt% LiNOa.

[0140] In a cylindrical Li-ion battery, the dense packing of the various layers in the jelly roll and volume changes during discharge-charge cycling may cause mechanical stresses and ageing of the battery. Volume changes may result from non-uniform lithium plating and dendrite formation at the anode, polysulfide “shuttle effect” and growth of solid electrolyte interfaces. Dendrites may even cause fires due to localized heating. Also, pit formation on the anode leads to non-homogenous transport of Li ions from the anode to the cathode and to fracture of the protective coating / layers disposed on the anode. Similarly, during the charging cycle, lithium dendrites may be formed on the metal anodes due to non-homogenous transport and deposition of Li ions from the cathode to the anode. Pitting and / or dendrite formation leads to uneven stresses and volumetric expansion of the jelly roll, which over time causes the layers of the roll to lose intimate contact with one another to exacerbate these issues and lead to accelerated degradation / capacity fade. Any one of the previously described CSC materials including any of the previously described rigid porous carbon agglomerates including metal nanoparticles may be used to mitigate the polysulfide shuttle effect and the effect of mechanical stresses and increase the cycle life of Li-S batteries.

[0141] As previously discussed, dense cathodes include tightly packed rigid porous carbon agglomerates with a cathode loading of at least 7 mg / cm2based on the total weight of carbonaceous materials, sulfur, binder, and other materials that are typically loaded on a cathode substrate. Additionally, “rigid porous carbon agglomerates” means porous carbon agglomerates of primary carbon nanoparticles that resist deformation under high shear mixing, for example, during preparation of a cathode slurry including the rigid porous carbon agglomerates or casting of a slurry including the rigid porous carbon agglomerates to produce one or more porous carbon layers or films on the cathode substrate. The rigid porous carbon agglomerates may resist deformation during shear mixing using a high shear mixer operating at speeds of at least 2000 rpm. Mixing speeds using the high shear mixer may be as high as 20,000 rpm. In some implementations, the rigid porous carbon agglomerates may resist deformation at shear rates of at least 500 s’1. In some other implementations, the rigid porous carbon agglomerates may resist deformation at shear rates of between approximately 200 s’1and 1000 s’1.

[0142] The rigid porous agglomerates may be sulfurized to form carbon-sulfur composites (“CSC”). The example dense cathodes as disclosed herein may increase the energy density of lithium-sulfur batteries. Additionally, rigid, and substantially spherical carbon agglomerates may improve dense packing of the porous carbon agglomerates and decrease resistance to electrolyte transport and lithium-ion conductivity through the one or more porous carbon layers disposed on a cathode substrate. In some implementations, an example lithium- sulfur battery cathode may include rigid porous carbon agglomerates of a predetermined average particle size (also referred to herein as average particle diameter). Tuning the average particle diameter of the rigid porous carbon agglomerates may increase cathode discharge capacity and battery cycle life as discussed below with reference to Figures 13A-13B.

[0143] Figure 13A shows a schematic diagram of a lithium-sulfur battery cathode 1300A including one or more porous carbon layers of rigid porous carbon agglomerates, according to some implementations. As can be seen, one or more carbon layers 1303A may be disposed on substrate 1301A. Substrate 1301A may include a cathode current collector. Each carbon layer 1303 A may include a plurality of rigid porous carbon agglomerates 1302A. The rigid porous carbon agglomerates 1302A may be substantially spherical in shape. Additionally, the rigid porous carbon agglomerates 1302A may be characterized by an average particle diameter (“dp,A”) 1305 A. The average particle diameter (“dp,A”) denotes the dso average particle diameter, where for example, a dso value of “x” pm indicates that 50% of rigid porous agglomerates in a sample subjected to particle size distribution analysis is less than “x” pm in diameter. Particle size distribution of rigid porous carbon agglomerate samples may be measured using one or more of laser diffraction, dynamic light scattering, dynamic image analysis, or sieve analysis.

[0144] As shown schematically in Figure 13 A, the carbon layers 1303 A including rigid porous carbon agglomerates 1302A present a tortuous pathway defined by the spacing between adjacent agglomerates 1302A for transport of the electrolyte 1304 A through the carbon layers 1303 A. As such, the electrolyte 1304A including lithium-ions may not be uniformly distributed within the carbon layers 1303 A to contact each of the agglomerates 1302A and facilitate the electrochemical reaction between sulfur dispersed or confined therein and the lithium ions (not shown for simplicity). This non-uniform distribution of electrolyte 1304A may result in a significant decrease of the cathode discharge capacity of lithium-sulfur batteries. Accordingly, rigid porous carbon agglomerates of a predeterminedaverage particle size may be needed to reduce tortuosity of the carbon layers in a lithiumsulfur battery cathodes. Those skilled in the art will appreciate that the thickness of the one or more porous carbon layers shown in Figure 13 A are shown by way of example only for illustration purposes, and that other scales may exist without departing from the scope and spirit of the present implementations.

[0145] Additionally, rigid porous carbon agglomerates 1302A of a predetermined average particle size may also reduce the intraparticle diffusion rate, that is, the diffusion rate within the agglomerates 1302A, of lithium-poly sulfides from the rigid porous carbon agglomerates 1302A to the electrolyte 1304A. As previously described, lithium-poly sulfides are formed by the electrochemical reaction of lithium-ions and sulfur dispersed or confined in the rigid porous carbon agglomerates and in the one or more carbon layers 1303 A. The lithium polysulfides may dissolve in the electrolyte and initiate the undesirable “shuttle effect.” Besides causing loss of active sulfur from the cathode, the lithium-polysulfides may diffuse to the anode, participate in solid electrolyte interface (“SEI”) formation reactions with the anode, increase the unevenness of SEI, and aggravate the corrosion of the lithium-metal or lithium-alloy anode. This cyclic shuttle effect results in the continuous leakage of active sulfur from the cathode, lithium corrosion at the anode, and leads to reducing coulombic battery efficiency. As such, decreasing the intraparticle diffusion rate of lithium-polysulfides in the rigid porous carbon agglomerates may confine the lithium polysulfides within the agglomerates 1302A, or within the layers 1303 A, increase the decomposition of lithium- polysulfides back to sulfur, and decrease sulfur leakage from the cathode. Mitigating the “shuttle effect” may improve the cycle life of lithium- sulfur batteries.

[0146] Figure 13B shows a schematic diagram of a lithium- sulfur battery cathode 1300B including one or more porous carbon layers of rigid porous carbon agglomerates, according to some implementations. Referring to Figure 13B, the one or more porous carbon layers 1303B may include rigid porous carbon agglomerates 1302B, which may be characterized by an average particle diameter (“dp,B”) 1305B. The average particle diameter (“dp,B”) denotes the dso average particle diameter. As shown schematically in Figures 13A-13B, dp,B is greater than dp,A. Additionally, increasing the average particle diameter dp,B of the rigid porous carbon agglomerates, may decrease the number of porous carbon layers 1303B required to achieve a targeted cathode loading (for e.g., 7 mg / cm2) disposed on substrate 1301B. Also, each carbon layer 1303B may include a fewer number of rigid porous carbon agglomerates 1302B compared to carbon layer 1303 A (referring to Figure 13 A) because dp,Bis greater than dp,A. The net beneficial effect of example cathode 1300B may include a decrease in tortuosity of the one of more porous carbon layers 1303B, an increase in wettability of the rigid porous carbon agglomerates 1302B by the electrolyte 1304B, and an increase in cathode discharge capacity.

[0147] Additionally, increasing the average particle diameter dp,B of the rigid porous carbon agglomerates 1302B may decrease the intraparticle diffusion rate of lithium poly sulfides, confine the lithium poly sulfides within the agglomerates 1302B, and mitigate the “shuttle effect.” Accordingly, in addition to an increase in cathode discharge capacity, the cycle life of the lithium-sulfur battery may also be increased by tuning the size of the rigid porous carbon agglomerates. In some implementations, rigid porous carbon agglomerates 1302B, may be characterized by an average particle diameter (“dp,B”) 1305B that is above or greater than a threshold average particle diameter (“dp,th”). Without being bound by any particular theory, and as described below with reference to Example 4 and Figure 13C, in some implementations, the threshold average particle diameter of the rigid porous carbon agglomerates to improve cycle life in lithium-sulfur batteries may be approximately 15 pm.

[0148] In some implementations, the rigid porous carbon agglomerates characterized by a predetermined average particle diameter as described above may be produced by spraying drying. Figure 14 shows an illustrative flowchart 1400 of an example single-step operation for producing a lithium- sulfur battery cathode including rigid porous carbon agglomerates of predetermined average particle diameter, according to some implementations. In some instances, operation 1400 may begin at 1402 with providing agglomerates of primary carbon nanoparticles produced by one or more of thermal cracking of hydrocarbons or microwave activation of hydrocarbons. Any one of the previously described agglomerates may be used at 1402. Example primary carbon nanoparticles may include primary carbon nanoparticles 805 or 905, as previously disclosed herein.

[0149] In some instances, the agglomerates may be surface etched at 1402 using methods that include CO2 etching to create pores on the external surface of the agglomerates and to increase the surface area of the carbon agglomerates. As previously described, surface etching methods may include one or more of steam etching, or etching using KOH, ZnCh or HNO3. At 1404, operation 1400 may continue with dispersing a predetermined amount of the agglomerates in a spray-drying solvent. An example solvent may include dimethyl formamide (“DMF”). In some implementations, the amount of agglomerates may beapproximately 2 wt% of the weight of the solvent. In some other implementations, the amount of agglomerates may be between approximately 1 wt% and approximately 6 wt% of the weight of the solvent.

[0150] At 1406, operation 1400 may continue with adding one or more polymeric binders in a suitable solvent (e.g., DMF) to the dispersion including the carbon agglomerates. The solution may be sonicated for a predetermined time. In some implementations, the amount of the one or more polymeric binders may be between approximately 5 wt% and 20 wt% of the weight of the agglomerates. In some implementations, the amount of the one or more polymeric binders may be approximately 10 wt% of the weight of the agglomerates.Alternately, steps 1404 and 1406 may be combined into a single step for producing a solution of polymeric binders and dispersed agglomerates of porous carbon primary nanoparticles in a solvent including polymeric binders. In some implementations, precursors of catalyst nanoparticles, as previously disclosed herein, may also be added at step 1406.

[0151] In some implementations, example polymeric binders may include one or more of styrene butadiene rubber, vinyl polymers, polyvinylidene fluoride, poly acrylic acid (“PAA”), carboxyl methyl cellulose, polyvinylpyrrolidone, polyvinyl acetate, polyacrylonitrile (“PAN”), polyethyleneimine (“PEI”), polymethylmethacrylate (“PMMA”), pitch, formaldehyde-based resins, or any combination thereof. Some binders such as PAN and PEI- 800 may be carbonized to binder residue, which may include trace levels of nitrogen. Other binders such as PMMA may completely burn-off while leaving behind no residue.

[0152] At 1408, operation 1400 may continue with spray drying the agglomerates dispersed in the solvent including polymeric binders at 1406 using a suitable spray dryer. For example, a spray dryer supplied by BUCHI (Delaware) may be used. At 1410, operation 1400 may continue with calcining the spray dried agglomerates at between approximately 800 °C and approximately 1200°C in the presence of argon as the atomizing gas, or a gas mixture of compressed dry air and one or more of argon or nitrogen, or an argon and hydrogen gas mixture. The operation 1400 atl410 may produce rigid porous carbon agglomerates including carbonized binder residue.

[0153] At 1412, operation 1400 may continue with determining the average particle diameter of the rigid porous carbon agglomerates produced at step 1410 and examining whether the average particle diameter (dso) of the rigid porous carbon agglomerates is above a predetermined threshold value (dso, th). Without being bound by any particular theory, insome implementations, the predetermined threshold value for the average particle diameter of the rigid porous carbon agglomerates may be approximately 15 pm.

[0154] If the average particle diameter (dso) of the rigid porous carbon agglomerates is equal to or below the predetermined threshold value (dso, th), operation 1400 may continue at 1414 with tuning spray drying parameters. In some instances, one or more of the atomizing gas flow rate, atomizing gas inlet temperature, or the amount of agglomerates or binders in the dispersion may be varied to increase the average particle diameter of the rigid porous carbon agglomerates produced at 1410. In some implementations, the atomizing gas inlet temperature may be between approximately 170 °C and approximately 210 °C. In some implementations, the atomizing gas inlet temperature may be approximately 190 °C. In some implementations, the atomizing gas flow rate may be between approximately 3 cc / min per gram of agglomerates (“cc / min / g”) and approximately 10 cc / min / g. In some implementations, the atomizing gas flow rate may be between approximately 2 cc / min / g and approximately 5 cc / min / g. In some implementations, rigid porous carbon agglomerates characterized by an average particle diameter (dso) below the predetermined threshold value (dso, th) may be binned, pelletized, and milled to desired size.

[0155] Alternately, if the average particle diameter (dso) of the rigid porous carbon agglomerates is above the predetermined threshold value (dso, th), operation 1400 may continue at 1416 with producing carbon-sulfur composites (“CSC”) by sulfurizing the rigid porous carbon agglomerates produced at 1410. In some instances, the sulfur to carbon weight ratio may be between approximately 1:5 and 10:1. In some other instances, the sulfur to carbon weight ratio may be approximately 3. At 1418, operation 1400 may continue with casting a slurry including the carbon-sulfur composites as one or more porous carbon layers or films on a suitable substrate to form the cathode in an example lithium-sulfur battery. The cathode substrate may include a cathode current collector. The cathode current collector may include aluminum. As previously noted, the packing density of the carbons including the example rigid porous carbon agglomerates may be at least approximately 7 mg / cm2when disposed as one or more porous carbon layers on a suitable cathode substrate.

[0156] In some implementations, the rigid porous carbon agglomerates may be produced using alternate methods to spray drying. In some implementations, an example process may include producing a slurry or mixture of agglomerates with a binder resin and carbonizing the slurry at a temperature of at least 500 °C. In some implementations, a formaldehyde-based resin may be used to produce the agglomerate-resin slurry. The resulting rigid porous carbonagglomerates may be in the form of carbon-based pellets and may be milled down to desired size. Etching is not a prerequisite for forming rigid porous carbon agglomerates. Rigid porous carbon agglomerates may be produced using unetched carbon agglomerates. The process conditions of these alternate methods may also be tuned to ensure that the average particle diameter (dso) of the rigid porous carbon agglomerates is above the predetermined threshold value (dso, th).EXAMPLES

[0157] In the Examples described below, a fluorinated ether electrolyte including approximately 50:25:25 (vol%) 1,2-dimethoxyethane (“DME”): 1,3-dioxolane (“DOL”): bis (2,2,2-trifluoroethyl) ether (“BTFE”) and including approximately 0.4 M lithium bis (trifluoromethanesulfonyl) LiTFSI and approximately 2 wt% LiNOs was used.EXAMPLE 1, Cathode discharge capacity and capacity retention of example lithium-sulfur coin cells assembled with cathodes including MgO catalyst nanoparticles in rigid porous carbon agglomerates.

[0158] Figures 3C-3D show plots 300C-300D illustrating cathode discharge capacity and capacity retention in lithium- sulfur coin cells with cathodes including MgO catalyst nanoparticles in rigid porous carbon agglomerates, according to some implementations. The loading of MgO in the rigid porous carbon agglomerates was approximately 8 wt%. The cathode capacity was approximately 4 mAh / cm2. The cathode density was 0.65 g / cc. The ratio of the capacities of the anode to cathode (“N / P ratio”) was approximately 2.6. Tests were conducted at C / 3 charge / discharge rate. The anode included lithium-metal with a thickness of approximately 80 pm. The E / S ratio in the example Li-S cells was approximately 5.

[0159] Referring to Figures 3C-3D, the lithium-sulfur cell including MgO disposed in the cathode porous carbon agglomerates was characterized by an improvement in cycle life of approximately 50% at approximately 80% capacity retention with cathode discharge capacity of at least approximately 450 mAh / g. Without being bound by any particular theory, catalyst nanoparticles including MgO dispersed in rigid porous carbon agglomerates may bind Li-PS intermediate compounds or convert these compounds to Li2S, which is insoluble in the electrolyte. As such, the resulting reduced concentration of Li-PS compounds in the electrolyte may mitigate the “shuttle effect” and increases cycle life of lithium-sulfur batteries.EXAMPLE 2, Cyclic voltammetry in lithium- sulfur cells with cathodes including rigid porous carbon agglomerates including MgO catalyst nanoparticles.

[0160] Cyclic voltammetry (CV) may provide insights into sulfur redox mechanisms in lithium-sulfur cells. Figure 3E shows cyclic voltammetry curves 300E of lithium-sulfur cells with cathodes including MgO catalyst nanoparticles in rigid porous carbon agglomerates, according to some implementations. Cyclic voltammetry curves were also measured using a reference cell including a cathode devoid of MgO nanoparticles for comparison. The cathode areal capacity in each case was approximately 5 mAh / cm2. The anode included a lithiummagnesium alloy anode. The N / P ratio was approximately 2. The MgO loading was approximately 8 wt%. Tests were conducted at a scan rate of 0.05 mV / s. The E / S ratio in the example lithium- sulfur cells was approximately 5.

[0161] Referring to Figure 3E, the sulfur reduction peaks at the cathode indicate that sulfur reduction at the cathode involves the generation of intermediate polysulfides, as previously discussed. A shift in the reduction potential to higher voltages and a reduction in cell polarization is observed with the lithium- sulfur battery cathode including MgO dispersed in the rigid porous carbon agglomerates. A reduction in cell polarization generally decreases the overpotential and mitigates the loss in energy density upon cycling, thereby improving the performance of lithium-sulfur batteries. Similarly, a shift in the oxidation potential to lower voltages with the lithium- sulfur battery cathode including MgO dispersed in the rigid porous carbon agglomerates also suggests reduced polarization of the cell. Additionally, the higher currents associated with the reduction peaks suggests higher conversion of lithium polysulfides during reduction at the cathode, thereby reducing the loss of electrolyte- soluble lithium polysulfides into the electrolyte, which in turn increases cyclic performance of the lithium-sulfur battery by mitigating the “shuttle effect.”EXAMPLE 3. Cathode discharge capacity of example lithium- sulfur coin cells assembled with cathodes including WC catalyst nanoparticles in rigid porous carbon agglomerates formed using various binder materials.

[0162] Figure 7B show a plot 700B illustrating cathode discharge capacity of lithiumsulfur coin cells with a cathode including WC catalyst nanoparticles in rigid porous carbon agglomerates, according to some implementations. The rigid porous carbon agglomerates including WC catalyst nanoparticles were formed using PAN, PMMA, and PEI as the binder materials using the example method 1000A (with reference to Figure 10A) previouslydescribed herein. The cathode capacity was approximately 4.5 mAh / cm2. The ratio of the respective capacities of the anode to cathode (“N / P ratio”) was approximately 2. The anode included lithium- metal with a thickness of approximately 80 pm. The E / S ratio in the Li-S cells was approximately 5.

[0163] Referring to Figure 7B, the cathode discharge capacity of a lithium-sulfur cell with a cathode including WC nanoparticles in rigid porous carbon agglomerates formed using PAN as the binder material was greater than 500 mAh / g through 100 cycles. This discharge capacity was also greater than the cells with cathode including WC nanoparticles in rigid porous carbon agglomerates formed using PMMA and PEI as binder materials. As previously described, rigid porous carbon agglomerates formed using PAN and PEI as binder materials using example method 1000A yielded WC nanoparticles of fine particle size which were uniformly dispersed on the surface of the agglomerates. However, the rigid porous agglomerates with WC nanoparticles formed using PEI as the binder were characterized by relatively lower BET surface area and pore volume compared to that corresponding agglomerates with WC catalyst nanoparticles formed using PAN binder material. The BET surface area of the rigid porous carbon agglomerates with WC catalyst nanoparticles formed using operation 1000A and using PAN and PEI binder materials was greater than 1000 m2 / g and less than 900 m2 / g, respectively. The pore volume of the rigid porous carbon agglomerates with WC catalyst nanoparticles formed using operation 1000A and using PAN and PEI binder materials was greater than 1.8 cc / g and less than 1.6 cc / g, respectively.

[0164] Without being bound by any particular theory, in addition to catalyst nanoparticle size and surface dispersion of the rigid porous carbon agglomerates, the electrochemical performance of lithium-sulfur coin cells with cathode porous carbon agglomerates including catalyst nanoparticles produced may also depend on one or more of the particle size or dispersion of the catalyst nanoparticles within the rigid porous carbon agglomerates.EXAMPLE 4, Capacity retention of example lithium- sulfur coin cells assembled with cathodes including rigid porous carbon agglomerates of predetermined particle size.

[0165] Figure 13C shows a plot 1300C illustrating the effect of average particle diameter of rigid porous carbon agglomerates at the cathode on capacity retention in lithium- sulfur coin cells, according to some implementations. Lithium- sulfur coin cells were assembled with cathodes including one or more porous carbon layers including rigid porous agglomerates with average particle size (dso) of approximately 15 pm and approximately 10 pm. The cathode areal capacity in each case was approximately 5 mAh / cm2. The anodeincluded a lithium-magnesium alloy anode. The N / P ratio was approximately 2.4. Tests were conducted at C / 3 charge / discharge rate.

[0166] The E / S ratio in the example lithium-sulfur cells was approximately 5, which is equivalent to E / S of approximately 3 in a pouch cell due to dead space - the space around the sides of the electrode stack in a pouch cell.

[0167] Referring to Figure 13C, “Tl” denotes a test run with a lithium- sulfur coin cell including a cathode with one or more layers of rigid porous agglomerates with average particle size (dso) of approximately 15 pm. “T2” denotes a test run with a lithium- sulfur coin cell including a cathode with one or more layers of rigid porous agglomerates of average particle diameter (dso) of approximately 10 pm. As can be seen, Tl was characterized by a significant improvement in cycle life at approximately 70% capacity retention (“end of life”) and demonstrates the beneficial effects of increasing particle size of the rigid porous agglomerates on lithium- sulfur battery performance.EXAMPLE 5. Effect of spray dryer atomizing gas flow rate on average particle diameter of rigid porous carbon agglomerates.

[0168] Figure 15 shows a plot 1500 illustrating the effect of spray dryer atomizing gas flow rate on the average particle diameter of rigid porous carbon agglomerates, according to some implementations. Referring to Figure 15, the average particle diameter (dso) of rigid porous carbon agglomerates produced by spray drying was measured at four different atomizing gas flow rates. “Fl” denotes an atomizing gas flow rate of approximately 3 cc / min per gram of agglomerates (cc / min / g). “F3” and “F4” denote atomizing gas flow rates of between 6 cc / min / g and approximately 7.5 cc / min / g. “F2” denotes an atomizing gas flow rate of approximately 4.5 cc / min / g. As can be seen, the average particle diameter (dso) of the rigid porous agglomerates produced by spray drying may be increased by decreasing the flow rate of the atomizing gas. Additionally, the average particle diameter (dso) using atomizing gas flow rate “Fl” was approximately 20 pm.EXAMPLE 6. Cathode discharge capacity and capacity retention of example lithium-sulfur coin cells assembled with cathodes including rigid porous carbon agglomerates of predetermined particle size.

[0169] Figures 16A-16B show plots 1600A-1600B illustrating the effect of average particle diameter of rigid porous carbon agglomerates disposed as porous carbon layers on cathode discharge capacity and capacity retention in lithium- sulfur coin cells, according to some implementations. Lithium- sulfur (“Li-S”) coin cells were assembled with cathodesincluding one or more porous carbon layers including rigid porous agglomerates with average particle size (dso) of approximately 20 pm, approximately 10 pm, and approximately 5 pm. The cathode sulfur content in these cells was approximately 72 wt%. The cathode loading in these cells was approximately 7.5 mg / cm2. Tests were conducted at C / 3 charge / discharge rate. The cathode capacity was approximately 4 mAh / cm2.

[0170] The anode included lithium-metal. The E / S ratio in the example Li-S cells was approximately 5, and the N / P ratio was approximately 2.

[0171] Referring to Figures 16A-16B, “Tl”’ denotes a test run with a lithium- sulfur coin cell including a cathode with one or more layers of rigid porous agglomerates with average particle size (dso) of approximately 20 pm. “T2”’ denotes a test run with a lithium- sulfur coin cell including a cathode with one or more layers of rigid porous agglomerates with average particle diameter (dso) of approximately 10 pm. “T3”’ and “T4”’ denote tests run with lithium-sulfur coin cells including a cathode with one or more layers of rigid porous agglomerates with average particle diameter (dso) of approximately 5 pm. As can be seen, Tl’ was characterized by an improvement in cycle life of approximately 20% at approximately 95% capacity retention with cathode discharge capacity of at least approximately 640 mAh / g. Tl’ resulted in a discharge capacity increase of approximately 20 mAh / g over T2’. Without being bound by any particular theory, these tests suggest that a predetermined threshold value for the average particle diameter of the rigid porous carbon agglomerates in the cathode porous carbon layers may be approximately 15 pm for improving cathode discharge capacity and capacity retention with cyclic operation of lithium- sulfur batteries.EXAMPLE 7 , Cathode discharge capacity of example lithium- sulfur pouch cells assembled with cathodes WC catalyst nanoparticles in rigid porous carbon agglomerates.

[0172] Figure 17 show a plot 1700 illustrating cathode discharge capacity in lithiumsulfur pouch cells with a cathode including WC catalyst nanoparticles in rigid porous carbon agglomerates, according to some implementations. Pouch cells were assembled in a 5042 format and included 5 double-sided anodes, no single-sided anode, 4 double-side cathodes and 2 single-sided cathodes. The cathode areal capacity was approximately 4 mAh / cm2. The cathode density was increased to 0.7 g / cc by calendering. The ratio of the respective capacities of the anode to cathode (“N / P ratio”) was approximately 2.6. The anode included a lithium-magnesium alloy anode. The E / S ratio in the example Li-S cells was approximately 3.6.

[0173] Referring to Figure 17, the lithium-sulfur pouch cell including WC nanoparticle additives disposed in the one or more cathode layers w characterized by an improvement in cycle life (relative to the pouch cell including cathode layers without WC nanoparticles) at cathode discharge capacity greater than 400 mAh / g. Accordingly, nanoparticle catalyst additives may be included in the rigid porous agglomerates disposed as one or more cathode layers to optimize mechanical stability and electrochemical performance of lithium-sulfur cells.

[0174] As used herein, a phrase referring to “at least one of’ or “one or more of’ a list of items refers to any combination of those items, including single members. For example, “at least one of: a, b, or c” is intended to cover the possibilities of: a only, b only, c only, a combination of a and b, a combination of a and c, a combination of b and c, and a combination of a and b and c. Unless otherwise specified in this disclosure, for construing the scope of the term “about” or “approximately,” the error bounds associated with the values (dimensions, operating conditions etc.) disclosed is ± 10% of the values indicated in this disclosure. The error bounds associated with the values disclosed as percentages is ± 1% of the percentages indicated. The word “substantially” used before a specific word includes the meanings “considerable in extent to that which is specified,” and “largely but not wholly that which is specified.”

[0175] Various modifications to the implementations described in this disclosure may be readily apparent to persons having ordinary skill in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein.

[0176] Additionally, various features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination. As such, although features may be described above in combination with one another, and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0177] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flowchart or flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In some circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described components and systems can generally be integrated together in a single product or packaged into multiple products.

Claims

CLAIMSWhat is claimed is:

1. A lithium-sulfur battery cathode including: a cathode substrate; and one or more porous carbon layers disposed on the cathode substrate, the one or more porous carbon layers including: rigid porous carbon agglomerates of porous carbon primary nanoparticles; catalyst nanoparticles dispersed on and within the rigid porous carbon agglomerates; carbonized binder residue dispersed within the rigid porous carbon agglomerates; and sulfur dispersed within the rigid porous carbon agglomerates.

2. The lithium-sulfur battery of claim 1, wherein the rigid porous carbon agglomerates resist deformation at shear rates of at least 500 s'1during mixing of a slurry including the rigid porous carbon agglomerates in a high shear mixer.

3. The lithium-sulfur battery cathode of claim 1, wherein a respective porous carbon primary nanoparticle includes: an inner porous shell disposed about a center of the respective porous carbon primary nanoparticle and enclosing an inner porous carbon region; an outer porous shell enclosing an outer porous carbon region disposed between the inner shell and the outer shell; and an interconnected porous network disposed in and in fluid communication with the inner and outer carbon regions.

4. The lithium-sulfur battery cathode of claim 3, wherein the inner carbon region and the outer carbon region are characterized by an average pore size and an average pore density associated with each region.

5. The lithium-sulfur battery cathode of claim 4, wherein the average pore size decreases along a radial direction from the center to the outer porous shell.

6. The lithium-sulfur battery cathode of claim 3, further including one or more intermediate porous shells disposed between the inner porous shell and the outer porous shell, wherein each of the intermediate porous shells encloses a respective intermediate porous carbon region.

7. The lithium-sulfur battery of claim 1, wherein the rigid porous carbon agglomerates of porous carbon primary nanoparticles include one or more interconnected bundles of electrically conductive graphene layers.

8. The lithium-sulfur battery of claim 7, wherein the graphene layers are arranged as one or more stacks connected to each other and defining a 3D porous scaffold structure including mesopores.

9. The lithium-sulfur battery of claim 7, wherein the one or more stacks are disposed substantially orthogonal to each other.

10. The lithium-sulfur battery of claim 7, wherein the graphene layers are characterized by a linear dimension of between approximately 50 nm and 200 nm.

11. The lithium-sulfur battery of claim 7, wherein the graphene layers include one or more of single layer graphene (SLG), few layer graphene (FLG), or many layer graphene (MLG).

12. The lithium-sulfur battery cathode of claim 1, wherein the rigid porous carbon agglomerates are characterized by a Raman spectroscopy signature with an ID / IG ratio between approximately 0.95 and approximately 1.05.

13. The lithium-sulfur battery of claim 1, wherein the rigid porous carbon agglomerates are characterized by an electrical conductivity of between about 500 S / m and 20,000 S / m when compressed at a pressure of about 12,000 pounds per square inch (psi).

14. The lithium-sulfur battery cathode of claim 1, wherein the catalyst nanoparticles are metal-based or non-metal based.

15. The lithium-sulfur battery cathode of claim 1, wherein the catalyst nanoparticles include one or more of metal, metal oxide, metal carbide, metal nitride, or any combination thereof.

16. The lithium-sulfur battery cathode of claim 1, wherein the catalyst nanoparticles include MgO nanoparticles.

17. The lithium-sulfur battery cathode of claim 16, wherein an average size of the MgO nanoparticles is less than approximately 200 nm.

18. The lithium-sulfur battery cathode of claim 16, wherein a loading of the MgO nanoparticles in the rigid porous carbon agglomerates is between approximately 10 wt% and approximately 20 wt%.

19. The lithium-sulfur battery cathode of claim 16, wherein a loading of the MgO nanoparticles in the rigid porous carbon agglomerates is between approximately 1 wt% and approximately 50 wt%.

20. The lithium-sulfur battery cathode of claim 1, wherein the catalyst nanoparticles include tungsten carbide (WC) nanoparticles.

21. The lithium-sulfur battery cathode of claim 20, wherein an average size of the WC nanoparticles is between approximately 100 nm and 500 nm.

22. The lithium-sulfur battery cathode of claim 20, wherein a loading of the WC nanoparticles in the rigid porous carbon agglomerates is between approximately 10 wt% and approximately 20 wt%.

23. The lithium-sulfur battery cathode of claim 20, wherein a loading of the WC nanoparticles in the rigid porous carbon agglomerates is between approximately 1 wt% and approximately 50 wt%.

24. The lithium-sulfur battery cathode of claim 1, wherein the carbonized binder residue corresponds to calcined byproducts of one or more of styrene butadiene rubber, vinyl polymers, polyvinylidene fluoride, poly acrylic acid (PAA), carboxyl methyl cellulose, polyvinylpyrrolidone, polyvinyl acetate, polyacrylonitrile (PAN), polyethyleneimine (PEI), polymethylmethacrylate (PMMA), pitch, or formaldehyde-based resins.

25. The lithium-sulfur battery cathode of claim 1, wherein a sulfur to carbon weight ratio in the one or more one or more porous carbon layers is between approximately 1:5 and 10:1.

26. The lithium-sulfur battery cathode of claim 1, wherein a packing density of the one or more porous carbon layers is at least 7 mg / cm2.

27. The lithium-sulfur battery cathode of claim 1, wherein a thickness of the one or more porous carbon layers is between approximately 10 pm and approximately 200 pm.

28. The lithium-sulfur battery cathode of claim 1, wherein an average size of the porous primary carbon nanoparticles is between approximately 20 nm and approximately 50 nm.

29. The lithium-sulfur battery cathode of claim 1, wherein an average size of the rigid porous carbon agglomerates is between approximately 50 nm and approximately 500 nm.

30. The lithium-sulfur battery cathode of claim 1, wherein an average size of the rigid porous carbon agglomerates is at least 1 pm.

31. The lithium-sulfur battery cathode of claim 1, further including one or more of a lithium-ion conducting film or an electron conducting film disposed on the surface of the rigid porous carbon agglomerates.

32. The lithium-sulfur battery cathode of claim 27, wherein the lithium-ion conducting film includes one or more of lithium lanthanum zirconium oxide (LLZO), lithium3-glycidyloxypropanesulfonate (LiGPS), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium phosphorus oxynitride (LiPON), or any combination thereof.

33. A lithium- sulfur battery including: a lithium anode; the cathode of claim 1 disposed opposite to the anode; and a fluorinated ether electrolyte disposed between and in contact with the anode and the cathode.

34. The lithium-sulfur battery of claim 33, wherein the electrolyte includes one or more of lithium nitrate (LiNCE) or lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dissolved in mixtures of one or more of 1,2-dimethoxyethane (DME), 1,3-dioxolane (DOL), bis (2,2,2-trifluoroethyl) ether (BTFE) or 1,1,2,2-tetraethoxyethane (TEE).

35. The lithium-sulfur battery of claim 33, further including a separator disposed between the anode and the cathode.

36. The lithium-sulfur battery of claim 33, wherein the separator includes a microporous monolayer polypropylene membrane.

37. The lithium-sulfur battery of claim 33, wherein the separator includes a ceramics-coated material.

38. A method for fabricating a lithium- sulfur battery cathode, the method including: dispersing agglomerates of porous primary carbon nanoparticles in a solution including a catalyst precursor and one or more polymeric binders; spray drying the agglomerates dispersed in the solution; and forming rigid porous carbon agglomerates including dispersed catalyst nanoparticles and dispersed carbonized binder residue by calcining the spray dried agglomerates at between approximately 800 °C and approximately 1200 °C.

39. The method of claim 38, wherein the rigid porous carbon agglomerates resist deformation at shear rates of at least 500 s'1during mixing of a slurry including the rigid porous carbon agglomerates in a high shear mixer.

40. The method of claim 38, wherein the calcining process is conducted in the presence of argon, or a mixture of compressed dry air and one or more of argon or nitrogen, or argon and hydrogen gas mixture.

41. The method of claim 38, wherein the amount of one or more polymeric binders in the solution is between approximately 5 wt% and approximately 20 wt% of the weight of the agglomerates.

42. The method of claim 38, further including surface etching the agglomerates of porous carbon nanoparticles prior to the dispersing step.

43. The method of claim 42, wherein the surface etching includes one or more of CO2 etching, potassium hydroxide (KOH) etching, zinc chloride (ZnCh) etching or nitric acid (HNO3) etching.

44. The method of claim 38, further including producing carbon-sulfur composites (CSC) including the rigid porous carbon agglomerates.

45. The method of claim 44, further including casting a slurry including the carbon-sulfur composites as one or more layers on a cathode substrate.

46. The method of claim 45, further including one or more of drying or calendering the one or more layers disposed on the cathode substrate.

47. The method of claim 46, wherein the density of the one or more layers after calendering is at least approximately 0.45 g / cc.

48. A carbon material including: rigid porous carbon agglomerates of porous carbon primary nanoparticles; andcarbonized binder residue dispersed within the rigid porous carbon agglomerates, wherein the rigid porous carbon agglomerates resist deformation at shear rates of at least 500 s'1during mixing of a slurry including the rigid porous carbon agglomerates in a high shear mixer.

49. The carbon material of claim 48, further including catalyst nanoparticles dispersed on and within the rigid porous carbon agglomerates.

50. The carbon material of claim 48, wherein the catalyst nanoparticles include one or more of metal, metal oxide, metal carbide, metal nitride, or any combination thereof.

51. The carbon material of claim 48, wherein the carbonized binder residue further includes trace amounts of nitrogen.

52. The carbon material of claim 48, wherein the carbonized binder residue corresponds to calcined byproducts of one or more of styrene butadiene rubber, vinyl polymers, polyvinylidene fluoride, poly acrylic acid (PAA), carboxyl methyl cellulose, polyvinylpyrrolidone, polyvinyl acetate, polyacrylonitrile (PAN), polyethyleneimine (PEI), polymethylmethacrylate (PMMA), pitch, or formaldehyde-based resins.

53. A method for fabricating a lithium- sulfur battery cathode, the method including: dispersing agglomerates of porous primary carbon nanoparticles in a solution including a catalyst precursor and one or more polymeric binders to form a slurry; carbonizing the slurry at a temperature of at least 500 °C to form carbon-based pellets; and forming rigid porous carbon agglomerates including catalyst nanoparticles and carbonized binder residue dispersed within the rigid porous carbon agglomerates by milling the carbon-based pellets.

54. The method of claim 53, wherein the porous carbon primary nanoparticles include:an inner porous shell disposed about a center of a respective porous carbon primary nanoparticle and enclosing an inner porous carbon region; an outer porous shell enclosing an outer porous carbon region disposed between the inner shell and the outer shell; and an interconnected porous network disposed in and in fluid communication with the inner and outer carbon regions.

55. The method of claim 53, wherein the inner carbon region and the outer carbon region are characterized by an average pore size and an average pore density associated with each region.

56. The method of claim 53, wherein the average pore size decreases along a radial direction from the center to the outer porous shell.

57. A cathode associated with a lithium- sulfur battery, the cathode including: a cathode substrate; and one or more porous carbon layers disposed on the cathode substrate, the one or more porous carbon layers including: rigid porous carbon agglomerates of porous carbon primary nanoparticles; and one or more of sulfur or carbonized binder residue dispersed in the rigid porous carbon agglomerates, wherein the average particle diameter of the rigid porous carbon agglomerates (dso percentile) is greater than a threshold average particle diameter.

58. The cathode of claim 57, wherein the rigid porous carbon agglomerates resist deformation at shear rates of at least 500 s'1during mixing of a slurry including the rigid porous carbon agglomerates in a high shear mixer.

59. The cathode of claim 57, wherein the threshold average particle diameter is approximately 15 pm.

60. The cathode of claim 57, wherein a packing density of the one or more porous carbon layers is at least 7 mg / cm2.

61. The cathode of claim 57, wherein a thickness of the one or more porous carbon layers is between approximately 20 pm and approximately 200 pm.

62. The cathode of claim 57, wherein the porous carbon primary nanoparticles include: an inner porous shell disposed about a center of a respective porous carbon primary nanoparticle and enclosing an inner porous carbon region; an outer porous shell enclosing an outer porous carbon region disposed between the inner shell and the outer shell; and an interconnected porous network disposed in and in fluid communication with the inner and outer carbon regions.

63. The cathode of claim 62, wherein the inner carbon region and the outer carbon region are characterized by an average pore size and an average pore density associated with each region.

64. The cathode of claim 63, wherein the average pore size decreases along a radial direction from the center to the outer porous shell.

65. The cathode of claim 62, further including one or more intermediate porous shells disposed between the inner porous shell and the outer porous shell, wherein each of the intermediate porous shells encloses a respective intermediate porous carbon region.

66. The cathode of claim 57, wherein the rigid porous carbon agglomerates are characterized by an electrical conductivity of between approximately 500 S / m and 20,000 S / m when compressed at a pressure of approximately 12,000 pounds per square inch (psi).

67. The cathode of claim 57, wherein a sulfur to carbon weight ratio in the one or more one or more porous carbon layers is between approximately 1:5 and 10:1.

68. The cathode of claim 57, wherein the carbonized binder residue corresponds to calcined byproducts of one or more of styrene butadiene rubber, vinyl polymers,polyvinylidene fluoride, poly acrylic acid (PAA), carboxyl methyl cellulose, polyvinylpyrrolidone, polyvinyl acetate, polyacrylonitrile (PAN), polyethyleneimine (PEI), polymethylmethacrylate (PMMA), pitch, or formaldehyde-based resins.

69. The cathode of claim 57, further including catalyst nanoparticles dispersed within the rigid porous carbon agglomerates.

70. The cathode of claim 69, wherein the catalyst nanoparticles include MgO nanoparticles.

71. A method for fabricating a cathode associated with a lithium- sulfur battery, the method including: dispersing agglomerates of porous primary carbon nanoparticles in a solution including one or more polymeric binders; spray drying the agglomerates dispersed in the solution; and forming rigid porous carbon agglomerates including dispersed carbonized binder residue by calcining the spray dried agglomerates at between approximately 800 °C and approximately 1200 °C, wherein the average particle diameter of the rigid porous carbon agglomerates (dso percentile) is greater than a threshold average particle diameter.

72. The method of claim 71, wherein the threshold average particle diameter is approximately 15 pm.

73. The method of claim 71, further including producing carbon-sulfur composites (CSC) including the rigid porous carbon agglomerates.

74. The method of claim 71, further including casting a slurry including the carbon-sulfur composites as one or more porous carbon layers on a cathode substrate.

75. The method of claim 71, wherein the rigid porous carbon agglomerates resist deformation at shear rates of at least 500 s'1during mixing of the slurry including the rigid porous carbon agglomerates in a high shear mixer.

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