EP4728571A2

EP4728571A2 - Lithium-alloy anodes for lithium-sulfur batteries

Info

Publication number: EP4728571A2
Application number: EP24740682.0A
Authority: EP
Inventors: Ratnakumar Bugga; Jesse Baucom; You Li; Haoxuan YOU; Supriya KOUL; Yongtao Meng; Yunguang ZHU; Luigi Abbate
Original assignee: Lyten Inc
Current assignee: Lyten Inc
Priority date: 2023-06-15
Filing date: 2024-06-13
Publication date: 2026-04-22
Also published as: WO2024259126A3; CN121488328A; KR20260026050A; WO2024259126A2; TW202510383A

Abstract

Lithium-magnesium alloy anodes and fluorinated ether electrolytes for lithium-sulfur batteries. The lithium-magnesium alloy anodes include about 90 wt% lithium and 10 wt% magnesium. The lithium-magnesium alloy anodes include at least one anode protective coating. The electrolyte includes about 0.4M LiTFSi and about 2 wt% LiNO₃ in fluorinated ether solvents.

Description

LITHIUM- ALLOY ANODES FOR LITHIUM-SULFUR BATTERIES

RELATED APPLICATIONS

[0001] This Patent Application claims priority to U.S. Provisional Patent Application No. 63/521,161 entitled “FREESTANDING LITHIUM-ALLOY ANODES FOR LITHIUM-SULFUR BATTERIES” and filed on June 15, 2023, to U.S. Provisional Patent Application No. 63/539,050 entitled “FREESTANDING LITHIUM-ALLOY ANODES FOR LITHIUM-SULFUR BATTERIES” and filed on September 18, 2023, and to U.S. Provisional Patent Application No. 63/658,047 entitled “LITHIUM-ALLOY ANODES FOR LITHIUM-SULFUR BATTERIES” and filed on June 10, 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 lithium-sulfur batteries that can provide high specific energy and energy density combined with long cycle life.

DESCRIPTION OF RELATED ART

[0003] Recent developments in batteries allow consumers to use high- specific energy 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 section. 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 freestanding anode associated with a lithiumsulfur (“Li-S”) battery may include a lithium-magnesium alloy and a polymer coating including one or more of polyvinylidene fluoride (“PVDF”), pentaerythritol tetraacrylate (“PETEA”), or polyethylene glycol dimethacrylate (“PEGDMA”), or a combination thereof, disposed on the freestanding anode. An example lithium- magnesium alloy may include a 90 wt% lithium (Li)- 10 wt% magnesium (Mg) alloy. The thickness of the freestanding anode may be at least about 80 pm.

[0006] In some implementations, an example Li-Mg alloy may further include one or more of titanium, zirconium, zinc, calcium, gallium, aluminum, or indium as additional alloying elements. In some implementations, a thickness of the polymer coating on the freestanding anode may be between about 1 pm and about 10 pm.

[0007] In some other implementations, another example anode associated with a lithium-sulfur battery may include a reacted alloy layer disposed as a surface layer on the anode active material layer. A polymer coating may be disposed on the reacted alloy layer. Accordingly, an anode protective coating may include more than one layer, wherein each respective layer is characterized by a respective composition. In some implementations, an example reacted alloy layer may include alloys of lithium and one or more of tin, indium, gallium, or aluminum. In some instances, a thickness of the reacted alloy layer may be less than 1pm. In some other instances, an anode associated with a lithium- sulfur battery may include one or more of a freestanding anode or an anode supported on an anode current collector. In some implementations, an example polymer coating ay include one or more of poly vinylidene fluoride (“PVDF”), pentaerythritol tetraacrylate (“PETEA”) or polyethylene glycol dimethacrylate (“PEGDMA”), or a combination thereof.

[0008] In some implementations, another example anode associated with a lithium-sulfur battery may include an anode active material layer, and an anode protective coating disposed on the anode active material layer. The anode protective coating may include an ionic liquid entrapped within a polymer matrix. In some instances, the anode active material layer may include a 90 wt% Li- 10 wt% Mg alloy. In some other instances, the polymer matrix may include one or more acrylate groups or ethylene oxide groups. In some instances, the polymer matrix may include one or more monomers or oligomers. In some implementations, a thickness of the anode protective coating may be less than 10 pm. In some other implementations, an amount of ionic liquid entrapped in the polymer matrix may be between about 10 wt% and about 40 wt%.

[0009] In some implementations, a lithium-sulfur battery may include a freestanding anode including a 90 wt% Li-10 wt% Mg alloy, a polymer coating including one or more of PVDF, PETEA, or PEGDMA, or a combination thereof, disposed on the freestanding anode, a cathode, and a fluorinated ether electrolyte. In some implementations, the fluorinated ether electrolyte may include about 50:25:25 (vol%) 1,2-dimethoxyethane (“DME”): 1,3-dioxolane (“DOL”): bis (2,2,2- trifluoroethyl) ether (“BTFE”) and including about 0.4 M lithium bis (trifluoromethanesulfonyl) (“LiTFSI”) and about 2 wt% LiNOa. The thickness of the freestanding anode may be between about 50 pm and about 200 pm.

[0010] In some implementations, a freestanding anode including a Li-Mg alloy may further include one or more of titanium, zirconium, zinc, calcium, gallium, aluminum, or indium as additional alloying elements. The Li-Mg alloy may include about 90 wt% Li, and about 10 wt% of a magnesium- aluminum- zinc alloy. In some implementations, the magnesium-aluminum-zinc alloy may include magnesium alloy AZ31. In some implementations, the magnesium-aluminum-zinc alloy may include magnesium alloy AZ61. In some implementations, the Li-Mg alloy may include about 90 wt% Li, between about 5 wt% and about 9.5 wt% magnesium, and between about 0.5 wt% and about 5 wt% aluminum.

[0011] In some implementations, a cathode associated with a lithium-sulfur battery including a freestanding Li-Mg alloy anode may include one or more porous carbon layers including sulfur deposited on a cathode substrate. The cathode substrate may include an aluminum current collector substrate. In some instances, the one or more porous carbon layers may include 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 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. 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. The average pore size may decrease along a radial direction from the center to the outer porous shell. In some other implementations, 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. Each of the intermediate porous shells may enclose a respective intermediate porous carbon region. [0012] In some implementations, the porous carbon agglomerates may include one or more interconnected bundles of electrically conductive graphene layers. In some instances, the graphene layers may be arranged as one or more stacks connected to each other and define a 3D porous scaffold structure including mesopores. In some other instances, 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”). In some implementations, the 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).

[0013] In some implementations, porous carbon agglomerates may be characterized by a Raman spectroscopy signature with an ID/IG ratio between about 0.95 and about 1.05. In some implementations, the sulfur to carbon weight ratio in the one or more one or more porous carbon layers in an example Li-S battery cathode may be between approximately 1:5 and 10:1. In some implementations, the sulfur to carbon weight ratio may be about 3. In some other implementations, the packing density of the one or more porous carbon layers may be at least 7 mg/cm². In some implementations, the thickness of the one or more porous carbon layers may be between about 10 pm and about 200 pm. In some implementations, the average size of the porous primary carbon nanoparticles may be between about 20 nm and about 50 nm. In some instances, the average size of the porous carbon agglomerates may be between about 50 nm and about 500 nm. In some other instances, the average size of the porous carbon agglomerates may be at least 1 pm.

[0014] In some implementations, any one of the Li-S batteries previously described herein may include a separator disposed between the anode and the cathode. The separator may include a microporous monolayer polypropylene membrane. The separator may include a ceramics-coated material.

[0015] In some implementations, the geometrical shape of any one of the Li-S batteries previously described may be cylindrical. The cylindrical battery may be about 18 mm in diameter and about 65 mm in length. In some implementations, the cylindrical battery may be about 21 mm in diameter and about 70 mm in length. In some implementations, the cylindrical battery may be about 46 mm in diameter and about 80 mm in length.

[0016] In some implementations, a roll-to-roll method of forming one or more anode protective layers on an anode active material may include arranging one or more anode active material layers and one or more alloying metal layers as feed material layers to a calender, passing the feed material layers through the calender, wherein each surface of the one or more anode active material layers is configured to be in contact with the one or more alloying metal layers in the calender, and forming in situ a reacted alloy layer on each surface of the anode active material layer during calendering. The reacted alloy layer may be a reaction product of a reaction between the one or more anode active material layers and the one or more alloying metal layers.

[0017] In some implementations, a method of forming one or more protective layers on an anode active material may include forming a reacted alloy layer on each surface of the anode active material using one of the methods previously described herein and depositing a polymer coating on the reacted alloy layer formed on each surface of the anode active material. In some implementations, a thickness of the reacted alloy layer may be less than 1 pm. In some other implementations, the polymer coating may include one or more of pentaerythritol tetraacrylate (“PETEA”) or polyethylene glycol dimethacrylate (“PEGDMA”). In some implementations, a thickness of the polymer coating may be less than 1 pm.

[0018] In some implementations, a method of disposing an anode protective coating on an anode associated with a lithium sulfur battery may begin with preparing a coating solution by mixing precursors including one or more monomers or oligomers, an ionic liquid, one or more lithium salts, and a polymerization initiator in a solvent. The operation may continue with applying the coating solution to the anode and initiating the polymerization of the one or more monomers or oligomers. Excess solvent may be removed by drying. The operation may continue with forming a polymer matrix infused with the ionic liquid by curing the coating. In some instances, the amount of precursors in the coating solution is between about 3 wt% and about 30 wt%. In some other instances, a loading of the polymer matrix infused with ionic liquid on the anode may be between about 10 pg/cm² and about 600 pg/cm². [0019] 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

[0020] Figure 1A shows a schematic diagram of an example porous carbon primary nanoparticle, according to some implementations.

[0021] Figure IB shows a transmission electron microscopy (TEM) image showing aggregates of porous carbon primary nanoparticles, according to some implementations .

[0022] Figure 1C shows a TEM image of agglomerates of porous carbon primary nanoparticles, according to some implementations.

[0023] Figure ID shows a TEM image of surface etched agglomerates of porous carbon primary nanoparticles, according to some implementations.

[0024] Figure 2 shows a schematic diagram of another example porous carbon primary nanoparticle, according to some implementations.

[0025] Figure 3A shows a schematic diagram of a mesoporous carbon nanoparticle, according to some implementations.

[0026] Figure 3B shows a scanning electron microscopy (SEM) micrograph of agglomerates of porous carbon primary nanoparticles, according to some implementations .

[0027] Figure 3C shows a TEM micrograph of agglomerates of porous carbon primary nanoparticles, according to some implementations.

[0028] Figure 4 shows a schematic diagram depicting an example lithium-sulfur cylindrical battery, according to some implementations.

[0029] Figure 5A shows a schematic diagram of a lithium-sulfur battery anode including one or more protective layers disposed over an anode active material layer, according to some implementations.

[0030] Figure 5B shows a schematic diagram of a lithium- sulfur pouch cell anode including one or more protective layers, according to some implementations. [0031] Figure 6A shows a schematic diagram of an example roll-to-roll continuous method for forming a lithium anode active material layer sandwiched between reacted alloy layers, according to some implementations.

[0032] Figure 6B shows a schematic diagram of an example roll-to-roll continuous method for forming a reacted alloy layer on anodes supported on a current collector, according to some implementations.

[0033] Figure 7 shows a plot illustrating cyclic performance data of freestanding anodes including Li-Mg alloys in half or symmetric lithium-sulfur battery cells, according to some implementations.

[0034] Figures 8A-8C show plots illustrating formation cycling data of freestanding anode including Li-Mg alloys in example lithium-sulfur coin cells, according to some implementations.

[0035] Figure 8D shows a plot illustrating discharge capacity estimation as a function of lithium content remaining in freestanding anode including Li-Mg alloys after a single discharge in lithium-sulfur batteries, according to some implementations .

[0036] Figures 9A-9B show plots illustrating cathode discharge capacity and capacity retention of example lithium- sulfur (“Li-S”) coin cells including freestanding anode including Li-Mg alloys, according to some implementations.

[0037] Figures 10A-10B show plots illustrating Li-S coin cell performance at varying magnesium concentrations in freestanding anode including Li-Mg alloys, according to some implementations.

[0038] Figures 11 A-l IB show plots illustrating cathode discharge capacity and capacity retention of Li-S coin cells freestanding anode including Li-Mg alloys, according to some implementations.

[0039] Figure 12A shows an SEM micrograph of the surface of a freestanding Li- Mg alloy anode harvested from lithium-sulfur coin cells after the first discharge, according to some implementations.

[0040] Figure 12B shows a cross-sectional SEM micrograph of a freestanding Li- Mg alloy anode harvested from lithium-sulfur coin cells after the first discharge, according to some implementations. [0041] Figure 12C shows a cross-sectional SEM micrograph with energy- dispersive X-ray spectroscopy (EDS) elemental analysis of a freestanding Li-Mg alloy anode after first discharge, according to some implementations.

[0042] Figures 13A-13B show plots illustrating cathode discharge capacity and capacity retention of example lithium- sulfur pouch cells including freestanding Li-Mg alloy anode, according to some implementations.

[0043] Figures 14A-14B show plots illustrating cathode discharge capacity and capacity retention of lithium-sulfur coin cells with quaternary freestanding Li-Mg alloy anodes, according to some implementations.

[0044] Figures 15A-15B show plots illustrating columbic efficiency and discharge capacity retention of lithium- sulfur coin cells including ternary freestanding Li-Mg alloy anodes, according to some implementations.

[0045] Figure 16A shows a plot illustrating cathode discharge capacity and capacity retention of lithium-sulfur coin cells including freestanding Li-Mg alloy anodes including a protective anode layer, according to some implementations.

[0046] Figure 16B shows a plot illustrating cycle life and total energy delivered as a function of capacity retention lithium- sulfur coin cells including freestanding Li-Mg alloy anodes including a protective coating, according to some implementations.

[0047] Figures 17A-17B show plots illustrating cathode discharge capacity and capacity retention of lithium-sulfur coin cells including 90Li-Mg alloy anodes including at least one protective layer, according to some implementations.

[0048] Figures 18A-18B show plots illustrating cathode discharge capacity and capacity retention of lithium-sulfur coin cells including an anode protective coating, according to some implementations.

[0049] Figures 19 show a plot illustrating discharge capacity retention of lithiumsulfur coin cells including an anode protective coating, according to some implementations .

[0050] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION

[0051] 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.

[0052] 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.

[0053] In this disclosure, 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 primary carbon nanoparticles. The primary carbon nanoparticles may be connected together by one or more of van der Waals forces, covalent bonds, ionic bonds, metallic bonds, or by other physical or chemical interactions. A plurality of aggregates may be considered as an agglomerate. Agglomerates of primary carbon nanoparticles may be produced from one or more methods including thermal cracking of a hydrocarbon gas. An example porous carbon agglomerate of primary carbon nanoparticles may be characterized by a principal dimension of at least about 1 pm.

[0054] 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 sp² hybridized carbon atoms. Additionally, graphene has a Raman spectrum with two main peaks: a G-mode at approximately 1580 cm'¹ and a D mode at approximately 1350 cm'¹ (when using a 532 nm excitation laser). As used herein, carbonaceous materials may refer to materials containing or formed of one or more types or configuration of carbon.

[0055] Commercialization of lithium- sulfur (“Li-S”) batteries has been hampered by limited discharge/charge cycling of less than approximately 100 cycles. Root cause analysis suggests that Li-metal anode failure is a primary reason for cell failure. During cycling, the Li-metal 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 (or freestanding) Li-metal anodes. In a freestanding Li-metal anode, the anode is not supported on a metal substrate such as a copper current collector. Anode stability is further impacted by an unstable electrode-electrolyte interface and pulverization of the anode caused by volume changes during cycling, because lithium has a high oxidation potential (about 3.04V) and can react with almost any electrolyte solution, either in a solvent or in a salt form, to form a solid electrolyte interphase (“SEI”) layer.

[0056] The SEI layer is electronically insulating but ionically conductive to Li⁺ ions. As such, once the SEI layer is formed, additional undesirable reaction between the Li-metal anode and electrolyte may be blocked or partially blocked by the SEI layer. However, the SEI layer is generally non-uniform, which results in non-uniform current distribution during plating, and may cause uneven (or non-uniform) lithium deposition and anode cracking during cycling. Fresh lithium metal-anode may be exposed to the electrolyte resulting in the undesirable consumption of lithium for reformation of the SEI layer. The localized non-uniform lithium deposition and stripping may manifest as dendrites during plating and pits during stripping at the anode during charge/discharge cycles. Dendrites may cause serious safety problems and reduce the cyclability of lithium-ion batteries. Additionally, dendrites may be dislodged from the anode to form ‘dead’ zones of lithium. Lithium dendrites may penetrate through polyolefin separators or even polymer/solid electrolyte separators disposed between the anode and the cathode of a battery, and negatively impact the safety and performance of Li-ion batteries.

[0057] 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 lithium ions forming polysulfides. 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 (Li2S_x, 8 < x < 1). Polysulfides (“Li-PS”) may be formed during the battery discharge cycle as:

S₈ Li₂S₈ Li₂S₆ Li₂S₄ Li₂S₃^ Li₂S₂^ Li₂S . (1)

[0058] 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 as they are highly soluble in the electrolyte, which results in loss of sulfur and reduction in cathode capacity. 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. The higher polysulfides (Li2S₈ and Li2Se) may diffuse to the anode and may get reduced to lower polysulfides (Li2Se and Li2S₄), which subsequently get oxidized at the cathode. At the anode, the polysulfides participate in SEI formation, increase the unevenness of SEI, and aggravate the corrosion of the Li metal anode. This cyclic process commonly known as the polysulfide “shuttle effect” results in poor coulombic efficiency, and progressive leakage of active sulfur material from the cathode which also reduces the life cycle of the battery. Further, the conversion of elemental sulfur to Li2S_x sulfur 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.

[0059] 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 ratio). The N/P ratio may be defined as the ratio of reversible capacity (mAh) of the negative electrode (anode) to that of the positive electrode (cathode) assuming complete utilization of sulfur.

[0060] Accordingly, to mitigate the loss of conductivity due to dissolved Li-PS, an excess amount of electrolyte is used in Li-S batteries. Additionally, to mitigate lithium-metal loss due to SEI formation, pitting, and dendrite formation, an excess of lithium-metal is required at the anode. These requirements frustrate attempts to reach or exceed the specific energy target of 500 W-h/kg in Li-S batteries. Li-S batteries generally require an electrolyte to sulfur ratio (“E/S ratio”) of approximately 5 pL/mgS, and a N/P ratio of greater than 2. For comparison, the N/P ratio in commercial Li-ion batteries is between approximately 1.03 and 1.2. While the N/P ratio is important to offset the likely higher loss of anode material during cycling, the areal capacity (mAh/cm²) is also critical to reduce the current density and hence failure rate on the anode.

[0061] Li-S anodes generally use a current collector such as copper as an anode support. Copper adds significant weight to Li-S batteries and reduces the specific energy of the battery. Copper is also susceptible to corrosion by polysulfides. Accordingly, there is significant interest in developing substrate-free or freestanding anodes. However, freestanding anode in Li-S batteries is challenging due to the morphological and instability issues with the lithium-metal (100% lithium) anode. Freestanding anode alloy compositions that are stable under cyclic conditions in Li-S batteries and at low E/S ratios of approximately less than or equal to 5 for coin cells, and less than or equal to 3 for pouch cells are needed. Freestanding anode compositions that are stable under cyclic conditions in Li-S batteries and at N/P ratios of approximately less than 2 to realize battery specific energy of 500 W-h/kg are also needed. [0062] In some implementations, Li-alloys may be used as freestanding anodes instead of pure-lithium metal anodes to overcome the previously described anode instability issues related to volume change during cycling, and the high reactivity of the Li-metal anodes with the electrolyte and with polysulfides. Lithium may alloy with several metals including one or more of silicon, tin, magnesium, or aluminum. Li-alloy anodes may have higher electrode potential compared to lithium deposition and may hinder corrosion at the anode caused by reactions between the anode and poly sulfides and electrolytes. Meanwhile, the alloying element may function as a lithium host for lithium deposition or plating (during the charge cycle) absorb volume changes during cycling and help to stabilize the anode. The alloying element may form a stable surface film over the anode, which may reduce the non-uniform deposition of lithium during plating.

[0063] Some alloying elements with lithium may reduce the Li-S battery capacity (mAh) or voltage, and subsequently reduce battery specific energy. Additionally, some alloying elements, for example, silicon (Si), tin (Sn), and germanium (Ge), may undergo severe volume changes during lithiation (plating, during charge cycle) and de-lithiation (stripping during discharge) and may not be suitable candidates for a Li- S battery anode. With elements such as silicon and tin, lithium may form intermetallic compounds of the type Li_xM_y, which have a high degree of ionic bonding, and are, subsequently, brittle, and fragile. Some other lithium alloys such as lithium-aluminum alloys are reversible only over a limited composition range and may not be suitable for Li-S battery use.

[0064] In some implementations, alloying lithium with small amounts of magnesium (Mg) may improve the stability of Li-S battery anodes to reactions with the electrolyte and polysulfides and increase battery cycle life. In lithium-magnesium (“Li-Mg”) alloy anodes, the magnesium alloying element may provide structural integrity to the anode during volume changes associated with battery cycling, because magnesium does not undergo stripping and plating at the anode. Additionally, alloying lithium with small amounts of magnesium permits a free-standing anode design (without the need for a copper current collector substrate), which also increases battery specific energy.

[0065] Li and Mg have comparable atomic radii and form an extended single solid phase body centered cubic structure (also referred to herein as a BCC structure) alloy over a wide composition range of about 11.5-100 wt% lithium in Li-Mg alloys. Therefore, the capacity of a Li-Mg alloy anode may be tuned over a broad range free of any alloy phase change considerations. The Li-Mg alloy may provide a scaffoldlike structure, which may facilitate insertion and removal of Li⁺ ions during the charge/discharge cycling of a Li-S battery. The volume change related to the insertion of one mole of Li into Mg may be about 80% as calculated using Li-Mg alloy lattice parameters, which is much lower than the volume change related to the interaction of lithium with other alloying elements such as silicon, tin, and antimony. Li-Mg alloys are very ductile, which permit straightforward fabrication of electrodes by rolling and annealing. At Li-rich compositions of approximately 90%, no loss in battery voltage may be observed when replacing a Li-anode (100% lithium) with a Li- Mg anode, because lithium stripping and plating may occur close to 0 V. Additionally, as magnesium is lithiophilic, dispersed magnesium in Li-Mg anodes may serve as nucleation sites for uniform lithium deposition during the charge cycle. [0066] Since Li-Mg alloy anodes form relatively stable SEI interface (compared to Li-anodes), a comparatively smooth anode surface morphology may be realized during the cyclic operation of a Li-S battery. Additionally, a Li-Mg alloy matrix, poor in lithium, and with high electric and ionic conductivity, may be formed after Li stripping to provide an excellent anode current collector and host for subsequent Li plating. Accordingly, Li-Mg alloy anodes may be freestanding and may not require a separate anode current collector.

[0067] In some implementations, lithium rich Li-Mg alloys including at least approximately 90 at% Li (at least about 72 wt% Li) may be used as durable freestanding Li-Mg anodes for Li-S batteries. Increasing the magnesium content in Li-Mg alloy anodes is not desirable because an increase in the number of activation cycles to achieve high anode capacities may be required. Additionally, increasing the magnesium content in Li-Mg alloys may cause processibility issues during anode fabrication due to the increased hardness of magnesium.

[0068] In some implementations, an example Li-Mg alloy freestanding anode in Li-S batteries may include about 90 wt% lithium and about 10 wt% magnesium (hereinafter, the “90 wt% Li : 10 wt% Mg” or “90Li-Mg alloy”). For the sake of clarity, the 90Li-Mg alloy includes about 97 at% Li and about 3 at% Mg. [0069] Without being bound by any particular theory, improving the cycle life of Li-S batteries to above 200 cycles and at high battery specific energy (500 W-h/kg) may require the synergistic interactions of a Li-alloy anode that can operate at N/P ratios of approximately less than 2, and a suitable electrolyte that reduces electrolyte consumption and enables battery operation at E/S ratios of less than about 5 pL/mg.

[0070] In some implementations, a Li-S battery may include a freestanding anode including a Li-Mg alloy, a polymer coating disposed on the freestanding anode, a cathode, and a fluorinated ether electrolyte disposed in contact with the freestanding anode and the cathode. In some implementations, the electrolyte may include one or more of lithium nitrate (LiNOa) or lithium bis (trifluoromethanesulfonyl) imide (“LiTFSI”).

[0071] In some implementations of an example Li-S battery including Li-Mg alloy freestanding anodes, the concentration of LiTESI in the liquid fluorinated ether electrolyte may be between about 0.1M and about 2M. In some implementations, the concentration of LiNOa in the liquid fluorinated ether electrolyte may be between about 2 wt% and about 6 wt%. In some other implementations of an example Li-S battery including a Li-Mg alloy freestanding anode, the magnesium content in the Li- Mg alloy may be between about 5 wt% and about 15 wt%. In some implementations, the Li-Mg alloy may include about 90 wt% lithium and about 10 wt% Mg.

[0072] In some implementations, the thickness of the freestanding anode including a Li-Mg alloy may between about 50 pm and about 200 pm. In some implementations, the polymer coating disposed on the freestanding anode may include poly vinylidene fluoride (“PVDE”).

[0073] In some implementations, an example liquid fluorinated ether electrolyte in Li-S batteries including Li-Mg alloy freestanding anodes may include about 50:25:25 (vol%) 1,2-dimethoxyethane (“DME”): 1,3-dioxolane (“DOL”): bis (2,2,2- trifluoroethyl) ether (“BTEE”) and including about 0.4 M LiTESI and about 2 wt.-% LiNOa. In some other implementations, an example liquid fluorinated ether electrolyte in Li-S batteries including Li-Mg alloy freestanding anodes may include about 50:25:25 (vol%) DME : DOL: (1,1,2,2-tetraethoxyethane) (“TEE”) and including about 0.4 M LiTESI and about 2 wt% LiNOa.

[0074] In some implementations, an example electrolyte may include about 50:25:25 (vol%) DME : DOL: 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (“TFETFE”) and including about 0.4 M LiTFSI and about 2 wt% LiNOa. In some other implementations, an example electrolyte may include about 60:20:10:10 (vol%) DME : DOL: TEE: TFETFE and including about 0.4 M LiTFSI and about 2 wt% LiNO₃.

[0075] In some implementations, an example electrolyte may include about 50:25:25 (vol%) DME : DOL: l,l,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (“TTE”) and including about 0.4 M LiTFSI and about 2 wt% LiNO₃. In some implementations, an example electrolyte for use with Li-Mg alloy anodes in Li-S batteries may include LiTFSI at concentrations of between about 0.1 M and about 1 M, and LiNO₃ concentrations of between about 1 wt% and 6 wt%. In some other implementations, an example electrolyte may include about 50:25:25 (vol%) DME : DOL: 1 fluorinated 1,4-dimethoxylbutane (FDMB) and including about 0.4 M LiTFSI and about 2 wt% LiNO₃. In some other implementations, the electrolyte may include about 1.0 M LiTFSI in about 50:50 (vol%) DOL: BTFE.

[0076] Additives such as lithium nitrate (LiNO₃) in the electrolyte may dissociate to produce lithium cations (Li⁺). Alternately, additives such as LiTFSI in the electrolyte may dissociate to produce lithium cations (Li⁺) and TFSI" anions.

Additives in the electrolyte that may dissociate to lithium ions may also include one or more of lithium lanthanum zirconium oxide (“LLZO”), oxinitrides (e.g., lithium phosphorus oxynitride or “LIPON”), NASICON-type conductors (e.g., lithium aluminum titanium phosphate) or lithium tin phosphorus sulfide (“LSPS”).

[0077] In some implementations of an example Li-S battery, the alloying element in Li-Mg alloy freestanding anodes may include additional alloying elements to improve cyclic stability, without significantly sacrificing specific energy. That is, the additional alloying elements in Li-Mg alloy anodes may be used to achieve about 200 cycles at discharge capacity of at least 400 mAh/g (or about 600 mAh/g sulfur) at above 80% capacity retention. In some implementations, the anode in Li-S batteries may include a ternary alloy (e.g., an alloy of the form Li-Mg-x) or a quaternary alloy (e.g., an alloy of the form Li-Mg-x-y). In the example Li-Mg-x-y alloys, the “x” and “y” alloying elements may include one or more of titanium, zirconium, zinc, calcium, gallium, aluminum, or indium. Without being bound by any particular theory, the ternary or quaternary alloys may provide for more stable SEI formation at the anode. [0078] In some implementations, an example alloying element for lithium-alloy freestanding anodes may include a magnesium-aluminum-zinc alloy. In some implementations, the Li-alloy freestanding anode may include about 90 wt% Li, and about 10 wt% of a magnesium-aluminum-zinc alloy. In some implementations, the magnesium-aluminum-zinc alloy may include the magnesium alloy AZ31. The magnesium alloy AZ31 includes between about 94.5 wt% and about 97 wt% magnesium, between about 2.5 wt% and 3.5 wt% aluminum, between about 0.6 wt% and about 1.4 wt% zinc, below about 0.3 wt% silicon, and below about 0.2 wt% manganese.

[0079] In some implementations, an example Li-alloy freestanding anode for Li-S batteries may include about 90 wt% lithium and about 10 wt% magnesium alloy AZ31 (“90Li-AZ31”). In some implementations, the magnesium-aluminum-zinc alloy includes the magnesium AZ61 alloy. The magnesium alloy AZ61 includes between about 92 wt% and about 93 wt% magnesium, between about 5.8 wt% and about 7.2 wt% aluminum, between about 0.4 wt% and about 1.5 wt% zinc, about 0.1 wt% silicon, about 0.15 wt% manganese, about 0.05 wt% copper, and less than about 0.01 wt% of nickel, calcium, and iron.

[0080] An example Li-alloy anode for Li-S batteries may include about 90 wt% lithium and about 10 wt% magnesium alloy AZ61 (“90Li-AZ61”). In some instances, an example Li-alloy freestanding anode for Li-S batteries may include magnesium and aluminum as alloying elements. In other instances, an example Li- Mg-Al alloy anode may include about 90 wt% Li, between about 5 wt% and 9.5 wt% Mg, and between about 0.5 wt% and 5 wt% Al. In some other instances, an example Li-Mg-Al alloy anode may include about 90 wt% Li, about 5 wt% Mg, and about 5 wt% Al. In some other instances, an example Li-Mg-Al alloy anode may include about 90 wt% Li, about 8 wt% Mg, and about 2 wt% Al. In some implementations, an example Li-Mg-Al alloy anode may include about 90 wt% Li, about 9.5 wt% Mg, and about 0.5 wt% Al.

[0081] In some example implementations, any one of the previously described freestanding Li-Mg alloy anodes may be coated with a surface coating which may react with lithium in the alloy to form a protective layer and further improve the stability of the anode under cycling. In some aspects, the surface coating for freestanding Li-Mg alloy anodes may include a polyvinylidene fluoride (“PVDF”) coating layer. The thickness of the PVDF coating layer may be between about 1 pm and about 10 jam.

[0082] Without being bound by any particular theory, PVDF may react with lithium in the freestanding Li-Mg alloy anode to form LiF" ions dispersed in a polymeric matrix. The protective layer may improve and/or may be associated with an improvement of lithium ion (Li⁺) transport from and to the anode during cycling. Reducing lithium-containing dendritic growth from the anode of a Li-S battery may increase the charge rate, the discharge rate, the energy density, the cycle life, or any combination thereof. The polymeric matrix may partially trap TFSI anions produced by the dissociation of additives such as LiTFSI in the electrolyte.

[0083] In some implementations, the surface coating for freestanding Li-Mg alloy anodes may include one or more of a pentaerythritol tetraacrylate (“PETEA”) or polyethylene glycol dimethacrylate (“PEGDMA”). The thickness of the coating layer may be between about 1 pm and about 10 pm. In other implementations, the surface coating for freestanding Li-Mg alloy anodes may include PETEA and PEGDMA.

The thickness of the coating layer may be between about 1 pm and about 10 pm. In some other implementations, an example Li-S battery may include a freestanding 90Li-Mg alloy anode, a polymer coating including one or more of PETEA or PEGDMA disposed on the freestanding anode, and a fluorinated ether electrolyte in contact with the anode. An example fluorinated ether electrolyte may include 50:25:25 (vol%) of 1,2-dimethoxyethane (“DME”) : 1,3-dioxolane (“DOL”) : bis (2,2,2-trifluoroethyl) ether (“BTFE”), and including about 2 wt% LiNOa, and 0.4 M LiTFSI. In some implementations, the thickness of the freestanding anode may be about 100 pm.

[0084] In some implementations, any one of the previously described freestanding lithium metal or lithium alloy anodes may include a reacted alloy layer disposed between the anode active material layer (e.g., Li-Mg alloy) and a protective polymer coating disposed on the anode active material layer. Examples of protective polymer coatings for freestanding anodes were previously described herein. The reacted alloy layer may be formed as reaction product of the anode active material layer with an alloying metal layer. Without being bound by any particular theory, the reacted alloy layer may be selectively conductive to Li⁺ ions while blocking polysulfides from reaching the anode active material layer. The reacted alloy layer may also be stable to the various lithium-sulfur battery electrolyte compositions previously described herein. As such, one or more of the reacted alloy layer or the protective polymer coating may serve as anode protective layers in freestanding lithium metal or lithium alloy anodes and enhance the life and stability of the anode in lithium-ion batteries and/or lithium-sulfur batteries.

[0085] In some implementations, the cathode associated with any one of the Li-S batteries including freestanding Li-Mg alloy anodes may include one or more carbon layers or films of agglomerates of primary carbon nanoparticles (as described below) disposed on a substrate like aluminum. An example loading of cathode material including carbonaceous material, sulfur, and binders on the substrate may be between about 5 g/cm² and about 10 mg/cm². The porosity and surface area of the carbon cathode may be tuned to achieve a desired balance between increased sulfur loading and inhibiting the migration of polysulfides into and/or throughout the electrolyte. [0086] Figure 1A shows a schematic diagram 100A of an example porous carbon primary nanoparticle 105, according to some implementations. In some aspects, the porous primary carbon nanoparticle 105 may resemble carbon nano-onions (“CNOs”). As shown in the example of Figure 1 A, the porous primary carbon nanoparticle 105 may include a core (inner) porous carbon region 111 defined by a first porosity and enclosed within an inner porous shell 113. The inner porous carbon region 111, which may also be referred to herein as the first porosity region, may include a plurality of first pores 101 dispersed therein. An outer porous carbon region 112, which may also be referred to herein as the second porosity region, may be disposed between the inner porous shell 113 and an outer porous shell 110 and may include a plurality of second pores 102 dispersed therein. The inner porous carbon region 111 and the outer porous carbon region 112 may be interconnected by one or more of the first pores 101 or one or more of the second pores 102, thereby interconnecting the first and second porosity regions. That is, the inner porous carbon region 111 may be configured to be in fluid communication with the outer porous carbon region 112 through an interconnected porous network. The inner porous carbon region 111 may be defined by a first pore density, and the outer porous carbon region 112 may be defined by a second pore density that is similar to or different than the first pore density. [0087] Example porous primary carbon nanoparticle 105 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 116 of the nanoparticle 105 to the outer boundary 113 of the nanoparticle 105. In some other implementations, porous primary carbon nanoparticle 105 may be characterized by a range of pore sizes and pore distributions in each region. The first pores 101 may be configured to retain polysulfides 120, and the second pores 102 may provide pathways or channels for the transport of lithium ions (not shown for simplicity) into and from the porous primary carbon nanoparticles 105 and for pre-loading sulfur 124 into the nanoparticles.

[0088] Figure IB shows a transmission electron microscopy (“TEM”) micrograph 100B of aggregates 140 of porous primary nanoparticles 105, 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. Example carbon aggregates 140 may include an interconnected porous network disposed between adjacent carbon nanoparticles 105. Aggregate 140 may include a plurality of porous carbon primary nanoparticles 105 and, in some instances, may resemble a “string-of-pearls.” In some implementations, the size or principal dimension of aggregate 140 may be between about 50 nm and 500 nm.

[0089] Figure 1C shows a TEM image 100C of agglomerates 145 of porous primary carbon nanoparticles 105, according to some implementations. An agglomerate 145 of porous carbon primary nanoparticles 105 may be characterized by a surface area of less than about 3000 m²/g. In some implementations, an example agglomerate 145 may be spherical in shape. In some implementations, an agglomerate 145 may be of any shape, including one or more of spherical, spheroidal, dumbbell, cylindrical, elongated cylindrical type, rectangular prism, disk, wire, or irregular.

[0090] Figure ID shows a TEM image 100D of surface etched agglomerates 142 of porous primary carbon nanoparticles, according to some implementations.

Example agglomerates 145 may be surface etched using methods that include CO2 etching to create pores on the external surface of the agglomerates 145 and to increase the surface area of the carbon agglomerates 145 to yield surface etched agglomerates 142. After etching, the surface etched agglomerates 142 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 142 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. The surface etched agglomerates 142 may be assembled as rigid porous carbon agglomerates by processes including spray drying.

[0091] Figure 2 shows a schematic diagram 200 of another example porous primary carbon nanoparticle 205, according to some implementations. Example trizone porous primary nanoparticle 205 may include a first core (inner) carbon zone or region 251, nested within a second intermediate carbon zone or region 252, which in turn is nested within a third outer carbon zone or region 253. Example first zone 251 may include pores 261 having an average size or principal dimension (diameter, length width) of less than approximately 40 nm, the second zone 952 may include pores 262 having an average size or principal dimension of less than approximately 35 nm, and the third zone 253 may include pores 263 having an average size or principal dimension of less than approximately 30 nm. In some example implementations, pores 261 may be characterized as macropores, the pores 262 in the intermediate region 952 may be characterized as mesopores, and the pores 263 in the outer region 252 as micropores.

[0092] In some implementations, the principal dimension DI of first zone 251 may be less than approximately 100 nm, the principal dimension D2 may be less than approximately 150 nm, and the principal dimension D3 of third zone 253 may be approximately 200 nm. The relative dimensions, porosities, and electrical conductivities of the first zone 251, the second zone 252, and the third zone 253 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) 251 may have a density of carbons of less than approximately 1 g/cc. The third zone (outer zone) 253 bounded by the perimeter or outer shell 255 of particle 205 may have a density of carbons of approximately less than between 1 g/cc and 3.5 g/cc. The second zone (intermediate zone) 252 may have a density of carbons of between approximately 0.5 g/cc and 3 g/cc. Each of the zones 251, 252, and 253 may be characterized by an average pore size and an average pore density associated with each region. The average pore size associated with each of zones 251-253 may decrease along a radial direction from the center of the porous primary carbon nanoparticle 205 to the outer porous shell 255.

[0093] Agglomerates of porous primary carbon nanoparticles 105 and/or porous primary carbon nanoparticles 205 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 105 and/or porous primary carbon nanoparticles 205 may be characterized by a Raman spectroscopy signature with an ID/IG ratio of approximately between 0.95 and 1.05. In some implementations, 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.

[0094] The porous carbon agglomerates as described above may be used to produce carbon-sulfur composites (“CSC”) by sulfurizing the carbon agglomerates. 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 about 3. In some implementations, a slurry including the carbon-sulfur composites and one or more polymeric binders 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. In some instances, the cathode substrate may include a cathode current collector. In some other instances, the cathode current collector may include aluminum. The carbon agglomerates may resist deformation under high shear mixing, and therefore produce films or layers of carbon of desired porosity, thickness, and packing density. In some implementations, the cathode may be characterized by a packing density of carbon material on the substrate (including sulfur, binder, and other constituents) of at least about 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. In some implementations, porous carbon agglomerates of porous carbon primary nanoparticles may include few-layer graphene (“FLG”) nanoplatelets orthogonally joined to each other in a dimensional (3D) porous graphene scaffold structure. These agglomerates may also be included as three- dimensional graphene carbons (“3DG carbons.”)

[0095] Figure 3A shows a schematic diagram of a mesoporous carbon nanoparticle 300A, according to some implementations. In some implementations, mesoporous carbon nanoparticle 300A may include an interconnected bundle of electrically conductive graphene layers arranged to form a 3D open porous scaffold structure. Nanoparticle 300A and porous carbon agglomerates including nanoparticles 300A 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.

[0096] The carbon nanoparticles 300A may include three-dimensional (“3D”) multi-modal 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 reference, 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 300A may be characterized by a three-dimensional (“3D”) hierarchical porous structure including pores 380. In some aspects, at least a portion of the hierarchical porous structure may further define a 3D open porous scaffold structure 381.

[0097] The nanoparticle 300A may include one or more interconnected bundles 382 of electrically conductive graphene layers or sheets. Each interconnected bundle 382 may include one or more stacks 383 of graphene layers. Each stack 383 may include a plurality of graphene layers 386 that are generally stacked horizontally as more clearly shown in stack 384. One or more stacks 383 of graphene layers 386 may be arranged to form a 3D porous scaffold structure 381 including mesopores. That is, a plurality of stacks 383 of electrically conductive graphene layers 386 may be sintered together to define the 3D open porous scaffold structure 381 (which includes mesopores 380 in the example of Figure 3A). In some implementations, one or more of the stacks 383 may be connected substantially orthogonal to each other. The open porous scaffold structure 381 may be configured to provide electrical conduction between contact points (not shown for simplicity) of the stacks of graphene layers 386. In some implementations, each graphene layer 386 may be characterized by a diameter or linear dimension (“L_a”) of between approximately 50 nm to approximately 200 nm. In some implementations, the graphene stack 383 may include few layer graphene (“FLG”), which may be composed of 5 to 15 layers of graphene.

[0098] A plurality of porous carbon primary nanoparticles 300A 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 300A. 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 381, while confining sulfur, may also provide a host scaffold-type structure to manage volume expansion due to the formation of long chain poly sulfides.

[0099] In some implementations, sulfur may be confined in the pores 380 of open porous scaffold structure 381. In some implementations, sulfur may also be confined in the scaffold structure spaces 385 formed by orthogonally joined stacks 383 of graphene layers 384.

[0100] The porous carbon agglomerates described herein and characterized using Raman spectroscopy show a high degree of order and uniformity of structure. As previously noted, “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 sp² hybridized carbon atoms. Additionally, graphene has a Raman spectrum with two main peaks: a G-mode at approximately 1580 cm'¹ and 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.

[0101] In some implementations, the agglomerates 302 (referring to Figure 3B as discussed below) 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 microwave processes. The graphene platelets may be flexible as they may be fused with each other at sp³ type defects in a sp² graphene lattice structure.

[0102] Figure 3B shows a SEM micrograph 300B of agglomerates 302 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 302. Agglomerate 302 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.

[0103] In some implementations, the agglomerates 300B 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. The agglomerates may be characterized using Raman spectroscopy and show a high degree of order. The agglomerates 300B may be characterized by a Raman spectroscopy signature having an ID/IG ratio between approximately 0.95 and approximately 1.05.

[0104] Figure 3C shows a TEM micrograph 300C of porous carbon agglomerates, according to some implementations. As shown in Figure 3C, the 3D few-layer graphene (“FLG”) structure 304 is a porous carbon aggregate at a 50 nm scale. 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.

[0105] 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 (about 18 mm diameter x about 65 mm length), a 21700 (about 21 mm diameter x about 70 mm length) battery or a 4680 (about 46 mm diameter x about 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. For 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.

[0106] Figure 4 shows a schematic diagram 400 depicting an example cylindrical battery 400, according to some implementations. Battery 400 may include a shell 410 and a jelly roll 420. Shell 410 may have a longitude axis indicated as AA’ in Figure 4, and jelly roll 420 may be disposed along the longitudinal axis AA’ within shell 410. Jelly roll 420 may have a cross section in a circle, a rectangle, a square, a triangle, or any other geometric shapes. Jelly roll 420 may include an anode 422, a first barrier layer (or separator layer) 424, a cathode 426, and a second barrier layer 428, each in the form of a rollable sheet. Anode 422, first barrier layer 424, cathode 426, and the second barrier layer 428 may be laminated on top of one another. As such, anode 422 and cathode 426 may be separated by the first and the second barrier layers to avoid undesirable short circuiting within battery 400. In some other implementations, a center pin or mandrel (not shown in Figure 4 for simplicity) may be attached to an inner edge of anode 422, 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 420. Anode current collector 402 (in the event the anode is not a free-standing anode) and cathode current collectors 404 may be integrated into the anode and cathode layers, respectively.

[0107] In some implementations, anode 422, first barrier layer 424, cathode 426, and second barrier layer 428 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 420. Either anode 422 or cathode 426 current collectors may include a current collector tab, which may protrude out after the sheets are wounded into the jelly roll 420. Tab 423 may connect the anode 422 or the cathode 426 to a negative or positive terminal (not shown in Figure 4 for simplicity), respectively, via any suitable process including a mechanical welding process. In some implementations, tab 423 may be the cathode current collector tab. The anode current collector (not shown for simplicity) may be disposed at the outer edge of the jelly roll 420, and the cathode current collector tab 423 may be disposed approximately in the center of the jelly roll 420.

[0108] In some implementations, either electrode (e.g., the anode 422 or the cathode 426) may be arranged in a misalignment with the other electrode and the first and the second barrier layers 424 and 428 during the rolling process so that a portion 425 may protrude out of the jelly roll 420. In some aspects, an electron conductive glue (not shown in Figure 4 for simplicity) may be disposed within shell 410 at the top and bottom of shell 410. The protruding portion 425 may be connected to the negative or positive terminal of shell 410 via electron conductive glue, and thereby eliminates the need for a mechanical welding process. In some implementations anode 422, anode current collector (not shown), first barrier layer 424, cathode 426, cathode current collector 404 and the second barrier layer 428 may be laminated on top of one another. A center pin or mandrel (not shown in Figure 4 for simplicity) may be configured as the cathode terminal and may be attached to the cathode current collector 404. When disposed as a jelly roll, the anode current collector may be disposed at the outer edge of the jelly roll 420, and the cathode current collector 404 may be disposed approximately in the center of the jelly roll 420.

[0109] In various implementations, anode 422 may be any suitable material that is typically used as an anode in a Ei-S battery. For example, anode 422 may be a lithium foil or a lithium substrate. In some instances, anode 422 may include a current collector to support the lithium foil or the lithium substrate. In some aspects, the anode 422 may include free-standing Ei-alloy anodes.

[0110] In some implementations, cathode 426 may include one or more layers of films or CSC including any of the previously described porous carbon agglomerates including metal nanoparticles. Cathode 426 may be disposed on cathode current

- l- collector 404. The cathode films may coat both sides of a current collector, such as an aluminum foil, to provide the maximum cathode capacity. The cathode CSC including the 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 426 may include other suitable sulfur-containing materials, such as lithium sulfide.

[0111] Battery 400 may include an electrolyte (not shown in Figure 4 for simplicity) incorporated into the jelly roll 420. In some implementations, battery 400 may have a liquid electrolyte that may be added to shell 410 after jelly roll 420 is disposed in shell or casing 410. In some other implementations, battery 400 may include a non-aqueous electrolyte such as solid-state electrolyte, gel electrolyte, or polymer film electrolyte incorporated into jelly roll 420. For example, between the first and the second barrier layers 424 and 428, 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 424 and 428 may function as both a separator and a non-aqueous electrolyte film. The electrolyte may include any one of the electrolyte compositions previously described herein.

[0112] In some implementations, a microporous monolayer polypropylene membrane may be used as a separator disposed between the anode 422 and the cathode 426. The porosity of an example separator (e.g., Celgard^R 2500) may be about 55%. The separator may have a similar ionic conductivity as the electrolyte but may serve to reduce lithium dendrite formation. The separator may be formed from a ceramic containing material that does not chemically react with metallic lithium. As a result, the separator with ceramic containing material may be used to control lithium- ion transport through the pores dispersed across the separator, while concurrently preventing a short-circuit by impeding the flow or passage of electrons through the electrolyte. The separator layer may include a mechanical strength enhancer coated and/or deposited on the anode. The mechanical strength enhancer may provide structural support for the battery, may prevent lithium dendrite formation from the anode, and/or may prevent protrusion of lithium dendrite throughout the battery. In some exemplary implementations, ceramic particles may be impregnated in the microporous monolayer polypropylene membrane. In some exemplary implementations, the separator may include a ceramic coated separator.

[0113] In a cylindrical Li-ion battery, the dense packing of the various layers in the jelly roll 420 and volume changes during discharge-charge cycling may cause mechanical stresses and ageing of the battery 400. Volume changes may result from non-uniform lithium plating and dendrite formation at the anode, poly sulfide “shuttle effect” and growth of solid electrolyte interfaces. Dendrites may even cause fires due to localized heating. Also, pit formation on the anode 422 leads to non-homogenous transport of Li ions from the anode 422 to the cathode 426 and also 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 420, which over time causes the layers of the roll 420 to lose intimate contact with one another to exacerbate these issues and lead to accelerated degradation/capacity fade. Cathodes including any one of the previously described CSC materials including any of the previously described porous carbon agglomerates, Freestanding anodes including any one of the Li-Mg alloy compositions, and any one of the previously described electrolyte compositions may mitigate the polysulfide shuttle effect and the effect of mechanical stresses and increase the cycle life of Li-S batteries.

[0114] Figure 5A shows a schematic diagram of a lithium-sulfur battery anode 500A including one or more protective layers disposed over an anode active material layer, according to some implementations. Example anode 500A may include anode active material layer 503A, which may include any of the free-standing lithium alloy anode compositions previously described herein. In some implementations, anode active material layer 503A may include a 90Li-Mg alloy. In some aspects, anode active material layer 503A may also include freestanding lithium metal. In some implementations, anode 500A may include a reacted alloy layer 504A disposed on the anode active material layer 503A. In some implementations, reacted alloy layer 504A may be formed in situ by calendering the anode active material layer (also referred to herein as an anode active material foil) 503A with an alloying metal layer or foil that reacts with anode active material layer 503A during the calendering process. That is, the reacted alloy layer 504A may be disposed as a surface layer on the anode active material layer 503A. In some implementations, the alloying metal layer or foil may include one or more of tin, indium, gallium, or aluminum. Accordingly, in some implementations, the reacted alloy layer 504A may include one or more alloys having a general composition Li_xSn_y, Li_xIn_y, Li_xGa_y, or Li_xAl_y. In some implementations, the thickness of reacted alloy layer 504A may be less than 1 pm.

[0115] Since the reacted alloy layer 504A may be electronically conductive, during cycling of a lithium-sulfur, lithium will plate on the reacted alloy layer 504A, and the reacted alloy layer may assist with uniform lithium nucleation and prevent dendrite formation. To control plating and stripping, an ionic conductive protective polymer coating 505A may be disposed on the reacted alloy layer 504A. The protective polymer coating 505A may also serve to block polysulfides from reaching the anode active material layer 503A. As such, the reacted alloy layer 504A may be disposed between anode active material layer 503A and the protective polymer coating 505A. In some implementations, the protective polymer coating 505A may include poly vinylidene fluoride (“PVDF”). In some implementations, the protective polymer coating 505A may include one or more of pentaerythritol tetraacrylate (“PETEA”) or polyethylene glycol dimethacrylate (“PEGDMA”). In some implementations, the thickness of the protective polymer coating 505A may be less than 1 pm. In some implementations, the thickness of the protective polymer coating 505A may be between about 1 pm and about 10 pm.

[0116] Figure 5B shows a schematic diagram of a lithium- sulfur pouch cell anode 500B including one or more protective layers, according to some implementations. As can be seen, anode 500B may include anode active material layer 503B, and a protective layer including a reacted alloy layer and a protective polymer coating disposed on each surface 506B and 506B’ of anode active material layer 503B. That is, reacted alloy layer 504B may be disposed between surface 506B of the anode active material 503B and protective polymer coating 505B. Additionally, reacted alloy layer 504B may be disposed between surface 506B’ of the anode active material 503B and protective polymer coating 505B’.

[0117] Referring to Figure 5B, the reacted alloy layers 504B and 504B’ disposed on each surface of anode active material layer 503B may be formed in situ by calendering the anode active material layer or foil 503B sandwiched between alloying metal layers or foils. The alloying metal layers of foils may react with anode layer 503A during the calendering process to form a reacted alloy layer on each surface of anode layer 503B, as described below with reference to Figure 6A. In some implementations, the alloying metal layers or foils may include one or more of tin, indium, gallium, or aluminum. Accordingly, in some implementations, the reacted alloy layers 504B and 504B’ may include one or more alloys having a general composition Li_xSn_y, Li_xIn_y, Li_xGa_y, or Li_xAl_y. In some implementations, the thickness of reacted alloy layers 504B and 504B’ may be less than 1 pm.

[0118] Referring again to Figure 5B, the protective polymer coatings 505B and 505B’ disposed on the reacted alloy layers 504B and 504B’ respectively, may include polyvinylidene fluoride (“PVDF”). In some implementations, the protective polymer coatings 505B and 505B’ may include one or more of pentaerythritol tetraacrylate (“PETEA”) or polyethylene glycol dimethacrylate (“PEGDMA”). In some implementations, the thickness of each of the protective polymer coatings 505B and 505B’ may be less than 1 pm. In some implementations, the thickness of each of the protective polymer coating 505B and 505B’ may be between about 1 pm and about 10 pm.

[0119] Figure 6A shows a schematic diagram of an example roll-to-roll continuous method 600A for forming a lithium anode active material layer sandwiched between reacted alloy layers, according to some implementations. Example operation 600A may begin at 606A with providing an anode active material layer 603A disposed on a first alloying metal layer or foil 602A’ . The anode active material layer 603A may include lithium metal foil or foils including any one of the lithium-alloy compositions previously disclosed herein. The foils 603A disposed on 602A’ may be supported using one or more supply rolls (not for simplicity). The operation 600 A may continue at 607 A with providing a second alloying metal layer or foil 602A, which may be supported using one or more supply rolls (not shown for simplicity). At 608 A, the operation may continue with continuously feeding through one or more calenders, the anode active material layer 603A disposed on first alloying metal layer 602A’ and the second alloying metal layer 602A, such that the anode layer 603A is sandwiched between the first and second alloying metal layers 602A and 602A’, respectively. Those skilled in the art will appreciate that the operation of arranging and feeding the various layers to the one or more calenders are shown by way of example only, and that other options to arrange and supply the one or more layers for calendering may exist without departing from the scope and spirit of the present implementations.

[0120] Referring to Figure 6 A, a calender generally includes a pair of rolls, 601 A and 601 A’, which are configured to exert a predetermined pressure to compress and sandwich the anode active material layer 603A between the alloying metal layers 602A and 602A’. The rolls 601 A and 601 A’ may be heated. Without being bound by any particular theory, when subjected to elevated temperature and pressure during calendering, the operation 600A may end at 609A with forming a reacted alloy layer 604A and 604A’ on each surface of the anode active material layer 6033A by reacting the alloying metal layers 602A and 602A’ with each surface of the anode active material layer 603A. That is, the example operation 600A may end with forming an anode active material layer 603A sandwiched between reacted alloy layers 604A and 604A’ as the layers pass through the one or more calenders in a single pass-through mode.

[0121] As previously described herein, the alloying metal layers or lithium-alloy foils may include one or more of tin, indium, gallium, or aluminum. Accordingly, in some implementations, the reacted alloy layers 604A and 604A’ may include one or more alloys having a general composition Li_xSn_y, Li_xIn_y, Li_xGa_y, or Li_xAl_y. In some implementations, the thickness of reacted alloy layers 604A and 604A’ may be less than 1 pm. In some implementations, the thickness of the anode active material layer may be at least 50 pm. As such, the reacted alloy layers may be considered as surface layers disposed on each surface of the anode active material layer 603A. Those skilled in the art will appreciate that the thickness of the various layers shown in Figure 6A 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 .

[0122] In some implementations, reacted alloy layers 604A and 604A’ of submicron thickness may be formed by varying one or more of the thickness of the alloying metal layers 602A and 602A’, temperature of the rolls 601A and 601A’, calender pressure, or pass through rate (or line speed) of the layers through the calenders. Accordingly, in the example roll-to-roll (“R2R”) method 600A, the alloying metal may not penetrate into the anode active material layer 603A to form interconnected, three-dimensional lithium metal/lithium metal alloy integrated networks. Instead, the reacted alloy layers 604 and 604A’ are disposed as thin surface layers on the anode active material layer 603A. In some implementations, the penalty in specific energy (“W-h/kg”) and energy density (“W-h/L”) caused by the addition of the reacted alloy layers may be less than 1%.

[0123] In some implementations, a protective polymer coating may be disposed on each of the reacted alloy layers 604A and 604A’ to add an additional layer of protection to anode active material layer 603A. As previously described, the protective polymer coating may include one or more of polyvinylidene fluoride (“PVDF”), pentaerythritol tetraacrylate (“PETEA”) or polyethylene glycol dimethacrylate (“PEGDMA”). In some implementations, the thickness of the protective polymer coatings disposed on each reacted alloy layer may be less than 1 pm. In some implementations, the thickness of the protective polymer coatings disposed on each reacted alloy layer 604 and 604’ may between about 1 pm and about 10 pm. In some implementations, the protective polymer coating 505B and 505 B’ (referring to Figure 5B) may be applied using any suitable method including one or spray coating, or Micro-Gravure™ coating.

[0124] In some implementations, the example reacted alloy layers described above as a protective layer in freestanding anodes may also protect a lithium metal anode or a lithium alloy-anode supported on a current collector. An example anode current collector may include copper. Figure 6B shows a schematic diagram of an example roll-to-roll continuous method 600B for forming a reacted alloy layer on anodes supported on a current collector, according to some implementations. Example operation 600B may begin at 606B with providing a first anode active material layer 603B disposed on a first current collector 605B. The operation may continue at 607B with providing a second anode layer 603B’ disposed on a second current collectors 605B’, and with providing, at 608B, an alloying metal layer or foil 602B. Each of these layers may be supported using one or more supply rolls (not shown for simplicity). The first anode active material layer 603B and second anode active material layer 603B’ may include lithium foil or foils or layers including any one of the lithium-alloy compositions previously disclosed herein.

[0125] Referring to Figure 6B, the operation may continue at 609B with continuously feeding through one or more calenders the first anode active material layer 603B supported on current collector 605B, the second anode active material layer 603B’ supported on current collector 605B’, and the alloying metal layer or foil 602B. As previously described, a calender generally includes a pair of rolls, 60 IB and 601B’, which may be configured to exert a predetermined pressure to compress and urge the alloying metal layer 602B to contact each of the first anode active material layer 603B and second anode active material layer 603B as they pass through the rolls. In some implementations, one or more of the rolls 601B and 601B’ may be heated. The operation may end at 61 OB with forming reacted alloy layers 604B and 604B’ on the exposed surface of each anode active material layer 603B and 603B’ respectively (that is, on the anode active material layer surface not in contact with the current collector) when the alloying metal layer 602B reacts with the first anode active material layer 603B and second anode active material layer 603B’ during calendering.

[0126] In some implementations, the thickness of reacted alloy layers 604B and 604B’ may be less than 1 pm. In some implementations, the thickness of the anode active material layer may be at least 50 pm. As such, the reacted alloy layers 604A and 604B may be considered as surface layers disposed on the surface of each anode layer 603B and 603B’ not in contact with their respective current collectors. Those skilled in the art will appreciate that the thickness of the various layers shown in Figure 6B 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. Additionally, those skilled in the art will appreciate that the operation of arranging and feeding the various layers to the one or more calenders are shown by way of example only, and that other options to arrange and supply the one or more layers for calendering may exist without departing from the scope and spirit of the present implementations.

[0127] In some implementations, a protective polymer coating may be disposed on each of the reacted alloy layers 604B and 604B’ to add an additional layer of protection to each of the anode active material layers 603B and 1603B’. As previously described, the protective polymer coating may include one or more of polyvinylidene fluoride (“PVDF”), pentaerythritol tetraacrylate (“PETEA”) or polyethylene glycol dimethacrylate (“PEGDMA”). In some implementations, the thickness of the protective polymer coatings disposed on each reacted alloy layer may be less than 1 p m. In some implementations, the thickness of the protective polymer coatings disposed on each reacted alloy layer may between about 1 pm and about 10 pm.

[0128] As previously noted, lithium- sulfur batteries may include a high solvating electrolyte, that is, an electrolyte characterized by a high lithium-poly sulfide solubility. In some instances, example electrolytes may include a IM lithium bis (trifluoromethanesulfonyl) (“LiTFSI”) in a 1,2-dimethoxyethane (“DME”) - 1,3- dioxolane (“DOL”) solvent mixture including lithium nitrate (LiNOa) additives. DME is reactive with lithium, and during cycling, lithium alkoxy species may be formed, which have the tendency to decrease both coulombic efficiency and cycle life. The reaction between DME and lithium may contribute to continuous generation of a solid electrolyte interphase (“SEI”), which consumes both electrolyte and lithium metal. As such, the lithium- sulfur cells may fail due to high impedance when either of these components (electrolyte or lithium) are depleted.

[0129] In contrast to DME, an ionic liquid may be characterized by a significantly lower reactivity with lithium-metal. Moreover, the relatively low solubility of polysulfides in ionic liquids may mitigate anode corrosion by the polysulfides and therefore also reduce the polysulfide “shuttle effect.” However, this lower lithium-ion conductivity of lithium- sulfur batteries including ionic liquid electrolytes may result in a relatively low discharge capacity and a relatively high impedance. Accordingly, a balance between cycle life and discharge capacity is needed.

[0130] In some implementations, an example lithium- sulfur battery may include a high solvating liquid fluorinated ether electrolyte to increase the discharge capacity of the battery without decreasing anode stability. Anode stability may be improved by coating the anode (e.g., a lithium-magnesium alloy anode) with a polymer matrix that entraps an ionic liquid. The example anode protective coating may prevent the fluorinated ether electrolyte from contacting the anode.

[0131] Accordingly, in some implementations, an anode protective coating for a lithium-sulfur battery anode may include an ionic liquid entrapped within a polymer matrix. Without being bound by any particular theory, ionic liquids trapped in a polymer matrix may promote high Li⁺ ion conductivity and allow for increasing the film or coating thickness to realize a substantially uniform anode protective coating. That is, the anode coating need not be thin (about 1 micron or less) to offset low ionic conductivity of polymer matrix layers without an entrapped ionic liquid. Thin anode coatings are prone to crack with battery cycling. Additionally, ionic liquids may form a stable SEI and repel poly sulfides.

[0132] In some implementations, an ionic liquid entrapped in a polymer matrix may include lithium salts to improve the lithium-ion conductivity of the anode protective coating. In some instances, example lithium salts may include lithium bis(fluorosulfonyl)imide (“LiFSI”) or lithium bis(trifluoromethanesulfonyl)imide (“LiTFSI”). These salts may also form a stable SEI on the anode surface during battery formation. In some other instances, the ionic liquids may include sodium bis(trifluoromethanesulfonyl)imide (“NaTFSI”), which may enhance SEI formation to improve diffusivity of lithium-ions through the anode protective coating. In some other instances, the ionic liquids may include LiNOa to form an SEI and repel polysulfides from reaching the anode.

[0133] In some instances, an example anode protective coating may be in the form of a solid layer or a gel and may include an ionic liquid trapped between polymer layers and/or other similar porous materials.

[0134] In some implementations, a method for forming an anode protective coating including an ionic liquid trapped in a polymer matrix may include preparing a coating solution by mixing precursors including one or more monomers or oligomers, an ionic liquid, one or more lithium salts, and a polymerization initiator (e.g., UV or thermal initiator) in a solvent, applying the coating solution to the anode, initiating the polymerization of the one or more monomers or oligomers, removing the solvent by drying, and forming the polymer matrix infused with the ionic liquid by curing the coating.

[0135] In some implementations, an amount of precursors (also referred to herein as the “solids content”) in the anode protective coating solution may be between about 3 wt% and about 30 wt%. The solids content may be calculated as the difference between the total weight of the ionic liquid (including precursors) and the weight of solvent and may be expressed as a fraction of the total weight of the ionic liquid including other precursors, as a percentage value. Table 1 provides a listing of example components in an anode protective coating solution, according to some implementations. Dimethyl ether (“DME”) may be used as the solvent.

Table 1. Listing of example components and their respective roles in an anode protecting coating.

[0136] Accordingly, an anode protective coating including a polymer matrix with entrapped ionic liquid may be formed by applying a coating solution with one or more precursors or components as shown in Table 1. The respective roles of each precursor in the example anode protecting coating is also shown in Table 1. Polymerization may be initiated by UV light or by the application of heat. The anode protective coating may be dried and cured to form a uniform coating on an anode associated with a lithium-sulfur battery.

[0137] In some implementations, example photo initiators may include 2- hydroxy-2-methyl-l -phenyl propanone (“HMPP”) for ultraviolet light (UV) curing. In some other implementations, 2,2’-Azobis(2-methylpropionitrile) (“AIBN”) may be used as the initiator during thermal curing.

[0138] Without being bound my any particular theory, ionic conductivity in an electrolyte mixture (o, mS/cm) may be expressed by equation (2), as shown below: a = n . q . p . (2) where, n represents the number density of free charged species (per m³), q represents the charge of ions (C), and p represents ionic mobility (m²/V.s). As such, an anode protective coating including only a cross-linked polymer formed by curing one or more monomers may be characterized by low ionic mobility, and subsequently, low lithium-ion conductivity. Additionally, monomers are non-ionic species and are characterized by low number density of free charged species (n) and low charge of ions (q). Accordingly, a cross-linked polymer disposed as an anode protective coating without any ionic liquid entrapped in the polymer matrix would be characterized by low lithium-ion conductivity.

[0139] In some implementations, entrapping an ionic liquid, which includes an anion and a cation, in a polymer matrix may increase ionic mobility u) and the number density of free charged species (n), while providing for a solid or gel anode protective coating that inhibits contact between a high solvation electrolyte and the lithium anode in lithium-sulfur batteries.

[0140] In some implementations, an example polymer matrix in an anode protective coating may include one or more acrylate groups or ethylene oxide groups. In some instance, the ethylene oxide groups may dissociate the one or more lithium- salts included in the example anode protective coatings and improve the number density of free charged species (n). However, high concentration of Li- salts may form clusters resulting in low ionic mobility (p).

[0141] In some implementations, the polymer matrix in an anode protective coating may include one or more monomers or oligomers. In some instances, the one or more monomers or oligomers may include one or more of polyethylene glycol dimethacrylate (“PEGDMA”), pentaerythritol tetraacrylate (“PETEA”), polymethyl methacrylate (“PMMA”), polyethylene oxide (“PEO”), polyethylene glycol diacrylate (“PEGDA”), cross linked polymer pentaerythritol tetraacrylate - polyethylene glycol dimethacrylate (“PETEA-PEGDMA”), cross linked polymer poly(vinylidene fluoride-co-hexafluoropropylene) (“PVDF-HFP”), or other similar monomers or oligomers, or combinations thereof.

[0142] In some implementations, example cations associated with an anionic liquid trapped in a polymer matrix of an anode protective coating may include one or more of l-Ethyl-3-methylimidazolium (“Emim”), l-Butyl-3-methylimidazolium (“Bmim”), N-Propyl-N-methylpyrrolidinium (“Pym”), 1-Butyl-l- methylpyrrolidinium (“Pym ), 1 -Methyl- l-(2-methoxyethyl) pyrrolidinium (“Pyrnoi ), N-methyl-Npropylpiperidinium bis(trifluoromethanesulfonyl)imide (“PP13TFSI”), or 1 -butyl- 1-methylpiperidinium bis(trifluoromethylsulfonyl)imide (“PP14TFSI”), or other similar cations.

[0143] In some implementations, example anions associated with an ionic liquid trapped in a polymer matrix of an anode protective coating may include one or more of bis(fluorosulfonyl)imide (“FSI”), bis(trifluoromethanesulfonyl)imide (“TFSI”), or dicyanamide (“DCA”).

[0144] In some implementations, an example ionic liquid entrapped in a polymer matrix of an anode protective coating may include one or more of l-ethyl-3- methylimidazolium bis(fluorosulfonyl)imide (“EmimFSI”), N-Propyl-N- methylpyrrolidinium bis(fluorosulfonyl)imide (“PymFSI”), N-propyl-N- methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (“PymTFSI”), 1-Butyl-l- methylpyrrolidinium bis(fluorosulfonyl)imide (“PyruFSI”), 1 -Butyl- 1- methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (“PyruTFSI”), l-Ethyl-3- methylimidazolium dicyanamide (“Emim DCA”), or 1 -methyl- 1 -(2- methoxyethyl)pyrrolidinium bis(trifluoromethanesulfonyl)imide (“PyrnoiTFSI”).

[0145] In some implementations, an example anode protective coating may include salts including lithium bis(trifluoromethanesulfonyl)imide (“LiTFSI”), lithium bis(fluorosulfonyl)imide (“LiFSI”), sodium bis(fluorosulfonyl)imide (“NaFSI”), sodium bis(trifluoromethanesulfonyl)imide (“NaTFSI”), or lithium nitrate (“LiNO₃”).

[0146] In some implementations, a thickness of an example polymer matrix with entrapped ionic liquid within the polymer matrix and after curing may be less than about 10 pm. In some other implementations, an amount of ionic liquid entrapped in the polymer matrix may be between about 10 wt% and about 40 wt%. In some implementations, a loading of the polymer matrix with entrapped ionic liquid on the anode of a lithium-sulfur battery may be between about 10 pg/cm² and about 600 pg/cm². In some other implementations, an amount of precursors (also referred to herein as “solids content”) in the example anode coating solution may be between about 3 wt% and about 30 wt%. As previously noted, the solids content may be calculated as the difference between the total weight of the ionic liquid (including other precursors) and the weight of solvent and may be expressed as a fraction of the total weight of the ionic liquid including other precursors.

[0147] In some implementations, a lithium-sulfur battery may include a lithium- alloy anode, an anode protective coating disposed the anode, a cathode, and liquid fluorinated electrolyte. In some instances, the anode protective coating may include a polymer matrix and an ionic liquid entrapped within the polymer matrix and may disclose any one of the anode protective coatings previously described herein. In some instances, the liquid fluorinated electrolyte may include one or more of lithium nitrate (LiNCh) or lithium bis(trifluoromethanesulfonyl)imide (“LiTFSI”).

[0148] An example anode may include any one of the anodes previously described herein. In some instances, an example anode may be a freestanding anode. In some other instances, an example anode may be supported on an anode substrate or current collector. An example cathode may include any one of the cathodes previously described herein.

EXAMPLES

[0149] In the examples described below, the electrolyte used in the Li-S battery implementations include about 50:25:25 (vol%) DME: DOL: BTFE and including about 0.4 M LiTFSI and about 2 wt% LiNOa. For symmetric half-cell Li-S battery tests, the example electrolyte may include about IM lithium polysulfides, Li2Se.

EXAMPLE. 1, Cyclic performance data of freestanding 90Li-Mg alloy anode in half or symmetric Li-cells.

[0150] Figure 7 shows a plot 700 illustrating cyclic performance data of freestanding anode including Li-Mg alloys in half or symmetric lithium-sulfur battery cells, according to some implementations. In particular, Figure 7 provides a comparison of cyclic performance of freestanding 90Li-Mg alloy anode and freestanding Li-metal anode (100wt% Li anode) in half or symmetric Li-cells.

Referring to Figure 7, half-cell tests demonstrate that the cells including example 90Li-Mg alloy anode and the electrolyte described above showed improved cycle life performance compared to a cell including a Li-metal anode with the same electrolyte. At about 300 cycles, the half-cell with Li-metal anode showed increasing polarization (overpotential of about 100 mV), while the half-cell with 90Li-Mg alloy anode continued to show low polarization through about 400 hours, which is indicative of superior cyclic performance of the freestanding 90Li-Mg alloy anode even in the presence of polysulfides in the electrolyte.

EXAMPLE 2A, Formation cycling data of freestanding 90Li-Mg alloy anode and Li- metal anode in example Li-S coin cells at C/20 charge/discharge rate.

[0151] Figures 8A-8C show plots 8OOA-8OOC illustrating formation cycling data of freestanding anode including Li-Mg alloys in example lithium- sulfur coin cells, according to some implementations. Cycling data was collected using coin cells including freestanding 90Li-Mg alloy anode and Li-metal anode at C/20 charge/discharge rate. The formation (activation) cycles included two cycles at a C/20 rate. Battery formation includes the process of performing the initial charge/discharge operation on a newly assembled battery cell. The coin cells including the freestanding 90 Li-Mg alloy anode showed a lower discharge capacity of approximately 700 mAh/g during the first cycle.

[0152] Referring to Figure 8A, a small but noticeable inflection in the potential towards the end of discharge may be noticed, which may be indicative of slow kinetics from surface reactions or bulk diffusion to the surface. However, after activation during the first discharge, the capacity of the cells with 90Li-Mg alloy anode improved during the second cycle and was comparable to the capacity of coin cells with Li-metal anode. The overpotential during the charge cycle was found to be lower with the freestanding 90Li-Mg alloy anode, which may suggest facile nucleation and Li plating on 90Li-Mg alloy compared to Li-metal anodes due to potential mitigation of dendrite formation at the 90Li-Mg anode.

EXAMPLE 2B. Estimated Discharge capacity vs. lithium content remaining in freestanding Li-Mg anodes after a single discharge in example lithium- sulfur batteries at different initial anode thickness.

[0153] Figure 8D shows a plot 800D illustrating discharge capacity estimation as function of lithium content remaining in freestanding anode including Li-Mg alloys after a single discharge in lithium-sulfur batteries, according to some implementations. Referring to Figure 8D, at nominal capacities of at least about 4 mAh/cm², 90Li-Mg alloy freestanding anode of thickness greater than about 20 pm may preserve a BCC single phase solid solution of Li-Mg alloy during battery cycling. However, a freestanding 90Li-Mg alloy of at least 100 pm in thickness may be needed to preserve a lithium content at the anode of between about 70 wt% to 90 wt% of the initial lithium content at the anode during cyclic battery operation.

EXAMPLE 3. Discharge capacity and capacity retention of example Li-S coin cells with freestanding 90 Li-Mg alloy anode and Li-metal anode at E/S of about 5 and at C/3 rate. [0154] Figures 9A-9B show plots 900A-900B illustrating cathode discharge capacity and capacity retention of example Li-S coin cells including freestanding anode including Li-Mg alloys, according to some implementations. The freestanding 90Li-Mg alloy anode thickness was about 100 pm. The freestanding Li-metal anode thickness was about 80 pm. A Celgard 2500 separator was used between the cathode and anode. The cathode loading was between approximately 7.3 mg/cm² and approximately 7.4 mg/cm². The nominal capacity was about 4 (mAh/cm²) based on the amount of cathode active material. The N/P ratio was about 2. Referring to Figures 9A-9B, about 50% improvement in cycle life with an increase in the average number of cycles with the Li-metal anode (about 141 cycles) to about 210 cycles with the 90Li-alloy anode was observed. Further, the capacity degradation to 80% capacity even after about 140 cycles is more gradual with 90Li-Mg alloy anode, while capacity degradation was more precipitous with Li-metal anode. Without being bound by any particular theory, a Li-S battery including a 90Li-Mg alloy anode when used with a fluorinated ether electrolyte may improve battery cycling capability by at least 50%.

EXAMPLE 4, Li-S coin cell performance at varying Mg concentrations in freestanding Li-Mg alloy anodes on cyclic stability, initial capacity, and activation times at E/S of about 5 and at C/3 rate.

[0155] Figures 10A-10B show plots 1000A-1000B illustrating Li-S coin cell performance at varying magnesium concentrations in freestanding anode including Li-Mg alloys, according to some implementations. The impact of varying Mg concentrations in cells with freestanding Li-Mg alloy anodes on cyclic stability, initial capacity, and activation times at E/S of about 5 and at C/3 rate was examined. The thickness of the Li-Mg alloy anodes was approximately 100 pm. The cathode loading was approximately 7.2 mg/cm² and the cathode capacity in each case was approximately 4 mAh/cm². A Celgard 2500 separator was used between the cathode and anode. Referring to Figures 108A-10B, increasing the magnesium content to 28 wt% decreased initial discharge capacity and increased the battery activation time. The 72Li-Mg alloy (28 wt% Mg) required a long activation period based on the high number of cycles (about 100 cycles) required for the initial capacity to reach about 500 mAh/g discharge capacity. For the sake of clarity, 72Li-Mg alloy includes about 90 at% Li and about 10 at% Mg. Decreasing the magnesium content to 3.4 wt% decreased cyclic stability.

[0156] Without being bound by any particular theory, Li-S batteries with freestanding 90Li-Mg alloy with the electrolyte 50:25:25 (vol%) of DME: DOL: BTFE with about 0.4 M LiTFSI and about 2 wt% LiNOa may provide a good compromise between cyclic stability, initial maximum capacity, discharge capacity, capacity retention, and battery activation time at E/S of less than or equal to 5. Increasing the Mg content in Li-Mg alloy anodes above approximately 10 wt% may result in undesirable slow activation of Li-S batteries to achieve the targeted battery capacity (mAh/g).

EXAMPLE 5. Cathode discharge capacity and capacity retention of lithium- sulfur coin cells with freestanding 90Li-Mg alloy anodes at E/S of about 4 and at C/3 rate.

[0157] Figures 11A-11B show plots 1100A-1100B illustrating cathode discharge capacity and capacity retention of lithium-sulfur coin cells freestanding anode including Li-Mg alloys, according to some implementations. Tests were conducted using freestanding 90Li-Mg alloy at E/S of about 4 and at C/3 rate (charge and discharge). An example 90Li-Mg alloy anode of about 100 pm in thickness and Limetai anode of about 80 pm in thickness was used. The cathode loading was approximately 7.6 mg/cm². The cathode capacity in each case was approximately 4 mAh/cm². A Celgard 2500 separator was used between the cathode and anode.

[0158] Referring to Figures 11 A-l IB, Li-S discharge capacity of at least 400 mAh/g was measured at 80% capacity through about 175 cycles even at E/S of about 4. Capacity retention was found to be stable to cyclic operation even at the low E/S of about 4. About 95% improvement in cycle life, with an increase in the average number of cycles with the Li-metal anode (88 cycles) to about 172 cycles with the 90Li-Mg alloy anode was observed. Without being bound by any particular theory, Li-S batteries with freestanding 90Li-Mg alloy with the electrolyte 50:25:25 (vol%) of DME: DOL: BTFE with about 0.4 M LiTFSI and about 2 wt% LiNOa may provide a good compromise between cyclic stability, initial maximum capacity, cathode discharge capacity, capacity retention, and battery activation time at E/S ratio of about 4. At E/S ratio of about 3, Li-S coin cells with both 90Li-Mg allow anode and Li- metal anode performed poorly. EXAMPLE 6. Scanning Electron Microscopy (“SEM”) micrographs of the surface of a freestanding 90Li-Mg alloy anode (bottom) and Li-metal anode (top) from Li-S coin cells after the first discharge.

[0159] Figure 12A shows an SEM micrograph 1200A of the surface of a freestanding 90Li-Mg alloy anode harvested from lithium- sulfur coin cells after the first discharge, according to some implementations. Referring to Figure 12A, the 90Li-Mg alloy-anode harvested from the cells after the first discharge showed a smoother surface and less pitting than the surface of Li-metal anode. This suggests the formation of a robust, smoother, and compact SEI on the example 90Li-Mg alloy anode with no noticeable discontinuities and pinholes. The superior cycle life of 90Li-Mg alloy anodes may be attributed to the improved stability of 90Li-Mg alloy to anode-electrolyte interactions even in the presence of polysulfides dissolved in the electrolyte.

[0160] Figure 12B shows another cross-sectional SEM micrograph 1200B of a freestanding 90Li-Mg alloy anode harvested from lithium- sulfur coin cells after the first discharge, according to some implementations. Referring to Figure 12B, the example 90Li-Mg alloy-anode after the first discharge showed a more compact surface layer disposed over a porous “host” structure near the anode-electrolyte interface, which also suggests the formation of a more stable SEI with the 90Li-Mg alloy anode.

[0161] Figure 12C shows a cross-sectional SEM micrograph 1200C with energy- dispersive X-ray spectroscopy (EDS) elemental analysis of a freestanding Li-Mg alloy anode after first discharge, according to some implementations. As shown in Figure 10C, a high localized concentration of Mg was measured at the anode-electrolyte interface during EDS analysis of a cross sectioned 90Li-Mg anode sample. The high Mg content at the interface may suggest the formation of a more stable SEI with 90Li- Mg anode. Without being bound by any particular theory, the high Mg content may also suggest the ability of the 90Li-Mg anode to “self-regulate” Li-ion stripping to create more uniform Li-ion flux and a smoother interface after stripping. This may be explained by the increase in kinetic barrier for Li-ion diffusion in regions of localized Li depletion and Mg enrichment. EXAMPLE 7 , Comparison of cathode discharge capacity and capacity retention at C/3 rate (charge and discharge) of example lithium- sulfur pouch cells with freestanding 90Li-Mg alloy anodes and cells with Li-metal anodes.

[0162] Figures 13A-13B show plots 1300A-1300B illustrating cathode discharge capacity and capacity retention of example lithium- sulfur pouch cells including freestanding Li-Mg alloy anode, according to some implementations. Cathode discharge capacity and capacity retention were compared at C/3 rate (charge and discharge) of example lithium- sulfur pouch cells including freestanding 90Li-Mg alloy anodes and cells with freestanding Li-metal anodes. Specific energy of about 175 W-h/kg Li-S was achieved in pouch cells with Li-metal (100 wt% lithium) anode. [0163] In contrast, pouch cells with 100 pm thick 90Li-Mg alloy anodes were characterized by a specific energy of about 223 W-h/kg (28% increase over Li-metal anodes). Pouch cells with 200 pm thick 90Li-Mg alloy anodes were characterized by a lower specific energy of about 206 W-h/kg (18% increase). This result suggests that 100 pm thick 90Li-Mg alloy anodes are also preferable from the standpoint of battery specific energy because increasing the anode thickness also increases the weight of the anode. Cycle life at about 80% capacity retention with the 90Li-Mg anodes (at least 100 cycles) increased by at least 70% compared to cells with Li-metal anodes (about 60 cycles) in the electrolyte. Without being bound by any particular theory, freestanding 90Li-Mg alloy anodes of at least 100 pm in thickness may increase Li-S battery (pouch cells) specific energy by at least about 20%.

EXAMPLE 8. Cathode discharge capacity of lithium- sulfur coin cells including freestanding Li-Mg alloy anodes with binary and quaternary Li-Mg alloy compositions at C/3 discharge rate.

[0164] Figures 14A-14B show plots 1400A-1400B illustrating cathode discharge capacity and capacity retention of lithium-sulfur coin cells with quaternary freestanding Li-Mg alloy anodes, according to some implementations. Cathode discharge capacity and capacity retention of example lithium-sulfur coin cells were compared using 90Li-Mg alloy anodes, Li-metal anodes, and 90Li-AZ31 quaternary alloy anodes at C/3 charge/discharge rate. The anode thickness was between about 170 pm and about 200 pm. The cathode loading was between approximately 7.3 mg/cm² and 7.6 mg/cm². A Celgard PP2075 dry-processed polymer separator was used between the cathode and anode. The cathode capacity in each case was approximately 4 mAh/cm² and the E/S ratio was about 5. In Figures 14A-14B, the legend “SAM” and “MSE” denote two different suppliers of magnesium.

[0165] Referring to Figures 12A-12B, at 80% discharge capacity retention, the cyclic performance of the cells with the 90Li-AZ31 anode was comparable to that of the cells with the 90Li-Mg alloy anodes (about 200 cycles.). The cells with Li-Mg alloy anodes were more stable than the cells with the Li-metal anodes (about 100-125 cycles).

EXAMPLE 9. Cathode discharge capacity of lithium- sulfur coin cells including freestanding Li-Mg alloy anodes with ternary Li-Mg alloy compositions at C/3 discharge rate.

[0166] Figures 15A-15B show plots 1500A-1500B illustrating columbic efficiency and discharge capacity retention of lithium-sulfur coin cells including ternary freestanding Li-Mg alloy anodes, according to some implementations. Cathode discharge capacity, capacity retention, and CE (coulombic efficiency) ratio of example lithium- sulfur coin cells were compared using Li-metal anodes, and 90 wt% Li : 10 wt% Mg- Al ternary alloy anodes at C/3 charge/discharge rate. The example Li-Mg- Al alloy anodes included about 90 wt% Li, about 8 wt% Mg, and about 2 wt% Al and about 90 wt% Li, about 5 wt% Mg, and about 5 wt% Al. Referring to Figures 15A-15B, through about 55 cycles, the discharge capacity (mAh/g) and capacity retention of cells using the example Li-Mg- Al alloy anodes were comparable to that of cell using the 90Li-Mg anodes. Additionally, the CE ratio through about 100 cycles was also comparable.

EXAMPLE 10, Cathode discharge capacity and capacity retention of example lithium-sulfur coin cells with freestanding 90Li-Mg alloy anodes including a protective anode layer.

[0167] Figure 16A shows a plot 1600A illustrating cathode discharge capacity and capacity retention of lithium-sulfur coin cells including freestanding Li-Mg alloy anodes including a protective anode layer, according to some implementations. Cathode discharge capacity and capacity retention of example lithium-sulfur coin cells were compared using freestanding Li-metal anodes, 90Li-Mg alloy anodes, and freestanding 90Li-Mg alloy anodes with a polymer coating at C/3 charge/discharge rate, according to some implementations. Referring to Figures 16A-16B, “Gl” denotes a freestanding anode including 90Li-Mg alloy without any protective coating layer. “G2” denotes a freestanding 90Li-Mg alloy anode including a PVDF protective coating layer. “G3” denotes a freestanding 90Li-Mg alloy anode including a protective coating layer including PETEA and PEGDMA. The cathode loading was approximately 7.6 mg/cm². The cathode capacity in each case was approximately 4 mAh/cm². A Celgard 2500 separator was used between the cathode and anode. The E/S ratio in the example Li-S cells was about 5, (equivalent to E/S of about 3 in a pouch cell due to dead space - the space around the sides of the electrode stack in a pouch cell) and the N/P ratio was between about 2.0 and about 2.4.

[0168] Referring to Figure 16A-16B, Li-S cells with the protective coating layer including PETEA and PEGDMA significantly extended cycle life to about 300 cycles at about 70% capacity retention with cathode discharge capacity of at least about 400 mAh/g. Total energy delivered of about 4.5 W-h also improved by about 87.5% over the lifetime of the cells (70% capacity retention).

EXAMPLE 11 , Cathode discharge capacity and capacity retention of example lithium-sulfur coin cells assembled with 90Li-Mg alloy anodes including at least one anode protective layer.

[0169] Figures 17A-17B show plots 1700A-1700B illustrating cathode discharge capacity and capacity retention of lithium-sulfur coin cells including 90Li-Mg alloy anodes including at least one anode protective layer, according to some implementations. Lithium-sulfur (“Li-S”) coin cells were assembled with 90Li-Mg alloy anodes, 90Li-Mg alloy anodes with a protective polymer coating, and 90Li-Mg alloy anodes including a reacted alloy layer disposed between the alloy and a protective polymer coating. The reacted alloy layer included a lithium-indium alloy layer. The protective polymer coating included PETEA and PEGDMA. The estimated thickness of the protective polymer coating on a dry basis was less than about 1 pm.

[0170] Tests were conducted at C/3 charge/discharge rate. The cathode loading in the cells was approximately 7.6 mg/cm². The cathode capacity was approximately 4 mAh/cm². A Celgard PP2075 separator was disposed between the cathode and anode. The E/S ratio in the example Li-S cells was about 5, which is equivalent to E/S of about 3 in a pouch cell due to dead space - the space around the sides of the electrode stack in a pouch cell, and the N/P ratio was between about 2.4 and about 2.5. The electrolyte included a fluorinated ether electrolyte including about 50:25:25 (vol%) 1,2-dimethoxyethane (“DME”): 1,3-dioxolane (“DOL”): bis (2,2,2-trifluoroethyl) ether (“BTFE”) and including about 0.4 M lithium bis (trifluoromethanesulfonyl) LiTFSI and about 2 wt% LiNOa.

[0171] Referring to Figures 17A-17B, “Tl” denotes baseline cells including a 90Li-Mg alloy anode without any anode protective layer. “T2” denotes cells including a 90Li-Mg alloy anode including a PETEA and PEGDMA protective polymer coating layer. “T3” denotes cells including a 90Li-Mg alloy anode including a lithium-indium reacted alloy layer disposed between the active alloy material and a protective polymer coating. The lithium-sulfur coin cells (“T3”) including the lithium-indium reacted alloy layer disposed between the active alloy material (90Li- Mg) and a protective polymer coating were characterized by an improvement in cycle life of about 20% at about 80% capacity retention with cathode discharge capacity of at least about 450 mAh/g compared to the performance of both the baseline cells (“Tl”) and cells including 90Li-Mg alloy anodes with a protective polymer coating (“T2”).

EXAMPLE 12, Cathode discharge capacity of lithium-sulfur coin cells including freestanding Li-Mg alloy anodes with an anode protective coating.

[0172] Table 2 provides a listing of precursors associated with an example anode protective coating solution, according to some implementations. An example anode protective coating solution included about 30 wt% solids (or precursors) and about 70 wt% solvent. The coating solution was applied to a lithium-magnesium alloy anode by spray coating. The polymer matrix included polyethylene glycol dimethacrylate (“PEGDMA”). The coating loading on the anode was about 125 pg/cm². Curing of the anode coating precursors was performed using UV light. 2-hydroxy-2-methyl-l- phenyl propanone (“HMPP”) was used as the photo initiator for the curing process.

Table 2. Listing of example components, their respective roles, and amount (wt %) in an anode protecting coating solution.

[0173] Figures 18A-18B show plots 18OOA-18OOB illustrating cathode discharge capacity and capacity retention of lithium-sulfur coin cells including an anode protective coating, according to some implementations. A PEGDMA polymer matrix including entrapped ionic liquid was prepared using the precursor composition listed in Table 2 to form the anode protective coating. A commercial Celgard® PP2075 separator was disposed between the anode and the cathode. Lithium- sulfur battery coin cells included a 90wt% Li- 10 wt% Mg alloy anode and were cycled at C/3 charge/discharge rate. The E/S ratio was about 5 pL/mg.

[0174] Referring to Figures 18A-18B, the coin cells including the anode protective coating outperformed the reference coin cells as cathode discharge capacity of above 450 mAh/g at capacity retention greater 70% was measured through about 200 cycles.

[0175] Table 3 provides a listing of precursors for an example anode protective coating solution, according to some implementations. An example anode protective coating solution included about 3 wt% solids (or precursors) and about 97 wt% solvent. The coating solution was applied to a lithium-magnesium alloy anode by spray coating. The polymer matrix included polyethylene glycol dimethacrylate (“PEGDMA”). The coating loading on the anode was between about 16 pg/cm² and about 52 pg/cm². Curing of the anode coating precursors was performed using a thermal initiator, 2,2'-Azobis (2-methylpropionitrile) (“AIBN”) using 550 W - 1000 W heaters.

[0176] Figures 19 show a plot 1900 illustrating discharge capacity retention of lithium-sulfur coin cells including an anode protective coating, according to some implementations. A PEGDMA polymer matrix including entrapped ionic liquid was prepared using the composition listed in Table 3 below to form the anode protective coating.

Table 3. Listing of example components, their respective roles, and amounts (wt %) in an anode protecting coating solution.

[0177] A commercial Celgard® PP2075 separator was disposed between the anode and the cathode. The lithium-sulfur battery coin cells included a 90wt% Li-10 wt% Mg alloy anode and were cycled at C/2 charge/discharge rate. The E/S ratio was about 5 pL/mg. Referring to Figures 19, the coin cells including the anode protective coating outperformed the reference coin cells as cathode discharge capacity of above 500 mAh/g (not shown) at capacity retention greater 80% was measured through about 175 cycles.

[0178] 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.” [0179] 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. [0180] 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.

[0181] 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 program components and systems can generally be integrated together in a single product or packaged into multiple products.

Claims

CLAIMS What is claimed is:

1. A freestanding anode associated with a lithium-sulfur battery, the freestanding anode including: an anode active material layer including a lithium- magnesium (Li-Mg) alloy; and a polymer coating including one or more of poly vinylidene fluoride (PVDF), pentaerythritol tetraacrylate (PETE A), or polyethylene glycol dimethacrylate (PEGDMA) disposed on the anode active material.

2. The freestanding anode of claim 1, wherein a magnesium content in the Li-Mg alloy is between about 5 wt% and about 15 wt%.

3. The freestanding anode of claim 1, wherein the Li-Mg alloy includes about 90 wt% lithium and about 10 wt% Mg.

4. The freestanding anode of claim 1, wherein a thickness of the freestanding anode is between about 50 pm and about 200 pm.

5. The freestanding anode of claim 1, wherein the Li-Mg alloy further includes one or more of titanium, zirconium, zinc, calcium, gallium, aluminum, or indium as additional alloying elements.

6. The freestanding anode of claim 1, wherein the Li-Mg alloy includes about 90 wt% Li, and about 10 wt% of a magnesium- aluminum-zinc alloy.

7. The freestanding anode of claim 6, wherein the magnesium-aluminum- zinc alloy includes magnesium alloy AZ31.

8. The freestanding anode of claim 6, wherein the magnesium- aluminumzinc alloy includes magnesium alloy AZ61.

9. The freestanding anode of claim 1, wherein the Li-Mg alloy includes about 90 wt% Li, between about 5 wt% and about 9.5 wt% magnesium, and between about 0.5 wt% and about 5 wt% aluminum.

10. The freestanding anode of claim 1, wherein the Li-Mg alloy includes about 90 wt% Li, about 5 wt% magnesium, and about 5 wt% aluminum.

11. The freestanding anode of claim 1, wherein the Li-Mg alloy includes about 90 wt% Li, about 8 wt% magnesium, and about 2 wt% aluminum.

12. The freestanding anode of claim 1, wherein the Li-Mg alloy includes about 90 wt% Li, about 9.5 wt% magnesium, and about 0.5 wt% aluminum.

13. The freestanding anode of claim 1, wherein a thickness of the polymer coating is between about 1 pm and about 10 pm.

14. The freestanding anode of claim 1, further including a reacted alloy layer disposed on the anode active material layer, wherein the polymer coating is disposed on the reacted alloy layer.

15. The freestanding anode of claim 14, wherein the reacted alloy layer includes alloys of lithium and one or more of tin, indium, gallium, or aluminum.

16. The freestanding anode of claim 14, wherein a thickness of the reacted alloy layer is less than about 1 pm.

17. An anode associated with a lithium- sulfur battery, the anode including: an anode active material layer; a reacted alloy layer disposed as a surface layer on the anode active material layer; and a polymer coating disposed on the reacted alloy layer.

18. The anode of claim 17, wherein the anode comprises one or more of a freestanding anode or an anode supported on a current collector.

19. The anode of claim 17, wherein the anode active material layer includes one or more of lithium metal or a lithium- magnesium alloy.

20. The anode of claim 17, wherein the reacted alloy layer includes alloys of lithium and one or more of tin, indium, gallium, or aluminum.

21. The anode of claim 17, wherein the polymer coating includes one or more of poly vinylidene fluoride (PVDF), pentaerythritol tetraacrylate (PETEA), or polyethylene glycol dimethacrylate (PEGDMA).

22. An anode associated with a lithium- sulfur battery, the anode including: an anode active material layer; and an anode protective coating disposed on the anode active material layer, wherein the anode protective coating includes an ionic liquid entrapped within a polymer matrix.

23. The anode of claim 22, wherein the anode active material layer includes a 90 wt% Li- 10 wt% Mg alloy.

24. The anode of claim 22, wherein the polymer matrix includes one or more acrylate groups or ethylene oxide groups.

25. The anode of claim 22, wherein the polymer matrix includes one or more monomers or oligomers.

26. The anode of claim 25, wherein the one or more monomers or oligomers include polyethylene glycol dimethacrylate (PEGDMA), pentaerythritol tetraacrylate (PETEA), polymethyl methacrylate (PMMA), polyethylene oxide (PEG), polyethylene glycol diacrylate (PEGDA), cross linked polymer pentaerythritol tetraacrylate - polyethylene glycol dimethacrylate (PETEA-PEGDMA), or crosslinked polymer poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP).

27. The anode of claim 22, wherein the ionic liquid includes a cation including one or more of l-Ethyl-3-methylimidazolium (Emim), l-Butyl-3- methylimidazolium (Bmim), N-Propyl-N-methylpyrrolidinium (Pym), 1-Butyl-l- methylpyrrolidinium (Pym), 1 -Methyl- l-(2-methoxy ethyl) pyrrolidinium (Pymoi), N-methyl-Npropylpiperidinium (PP13), or 1 -butyl- 1-methylpiperidinium (PP14).

28. The anode of claim 22, wherein the ionic liquid includes an anion including one or more of bis(fluorosulfonyl)imide (FSI), bis(trifluoromethanesulfonyl)imide (TFSI), or dicyanamide (DC A).

29. The anode of claim 22, wherein the ionic liquid includes one or more of l-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EmimFSI), N-Propyl-N- methylpyrrolidinium bis(fluorosulfonyl)imide (PymFSI), N-propyl-N- methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PymTFSI), 1 -Butyl- 1- methylpyrrolidinium bis(fluorosulfonyl)imide (PymFSI), 1-Butyl-l- methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PymTFSI), l-Ethyl-3- methylimidazolium dicyanamide (Emim DCA), or 1 -methyl- 1 -(2- methoxyethyl)pyrrolidinium bis(trifluoromethanesulfonyl)imide (PymoiTFSI).

30. The anode of claim 22, wherein the anode protective coating further includes one or more salts including lithium bis(trifluoromethanesulfonyl)imide (EiTFSI), lithium bis(fluorosulfonyl)imide (EiFSI), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), or lithium nitrate (EiNO₃).

31. The anode of claim 22, wherein a thickness of the anode protective coating is less than 10 pm.

32. The anode of claim 22, wherein an amount of ionic liquid entrapped in the polymer matrix is between about 10 wt% and about 40 wt%.

33. A lithium- sulfur battery including: a freestanding anode including a 90 wt% Li- 10 wt% Mg alloy; a polymer coating including one or more of poly vinylidene fluoride (PVDF), pentaerythritol tetraacrylate (PETE A), or polyethylene glycol dimethacrylate (PEGDMA) disposed on the freestanding anode; and a fluorinated ether electrolyte including one or more of one or more of lithium bis (trifluoromethanesulfonyl) (LiTFSI), or LiNOa.

34. The lithium-sulfur battery of claim 33, wherein a thickness of the freestanding anode is about 100 pm.

35. The lithium-sulfur battery of claim 33, wherein a concentration of LiTFSI in the electrolyte is between about 0.1 M and about 2 M.

36. The lithium-sulfur battery of claim 33, wherein a concentration of LiNO₃ in the electrolyte is between about 2 wt% and about 6 wt%.

37. The lithium-sulfur battery of claim 33, wherein the fluorinated electrolyte includes one or more of: about 50:25:25 (vol%) 1,2-dimethoxyethane (DME): 1,3-dioxolane (DOL): bis (2,2,2-trifluoroethyl) ether (BTFE) and including about 0.4 M LiTFSI and about 2 wt% LiNO₃; about 50:25:25 (vol%) DME : DOL: 1,1,2,2-tetraethoxyethane (TEE) and including about 0.4 M LiTFSI and about 2 wt% LiNOa; about 50:25:25 (vol%) DME : DOL: 1,1,2,2-tetrafluoroethyl 2,2,2- trifluoroethyl ether (TFETFE) and including about 0.4 M LiTFSI and about 2 wt% LiNO_3; about 60:20:10:10 (vol%) DME : DOL: TEE: TFETFE and including about 0.4 M LiTFSI and about 2 wt% LiNO₃; about 50:25:25 (vol%) DME : DOL: l,l,2,2-tetrafluoroethyl-2,2,3,3- tetrafluoropropyl ether (TTE) and including about 0.4M LiTFSI and about 2 wt% LiNO₃; about 50:25:25 (vol%) DME : DOL: 1 fluorinated 1,4-dimethoxylbutane (FDMB) including about 0.4 M LiTFSI and about 2 wt% FiNCh; or about 1.0 M FiTFSI in about 50:50 (vol%) DOF: BTFE.

38. The lithium-sulfur battery of claim 33, further including a cathode including: a cathode substrate; one or more porous carbon layers including sulfur disposed on the cathode substrate, the one or more porous carbon layers including porous carbon agglomerates of porous carbon primary nanoparticles, 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.

39. The lithium-sulfur battery of claim 38, 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.

40. The lithium-sulfur battery of claim 39, wherein the average pore size decreases along a radial direction from the center to the outer porous shell.

41. The lithium-sulfur battery of claim 38, 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.

42. The lithium-sulfur battery of claim 38, wherein the porous carbon agglomerates include one or more interconnected bundles of electrically conductive graphene layers.

43. The lithium-sulfur battery of claim 42, wherein the graphene layers are arranged as one or more stacks connected to each other and defining a 3D porous scaffold structure including mesopores.

44. The lithium-sulfur battery of claim 43, wherein the one or more stacks are disposed substantially orthogonal to each other.

45. The lithium-sulfur battery of claim 42, wherein the graphene layers are characterized by a linear dimension of between approximately 50 nm and 200 nm.

46. The lithium-sulfur battery of claim 42, wherein the graphene layers include one or more of single layer graphene (SLG), few layer graphene (FLG), or many layer graphene (MLG).

47. The lithium-sulfur battery of claim 38, wherein the porous carbon agglomerates are characterized by a Raman spectroscopy signature with an ID/IG ratio between about 0.95 and about 1.05.

48. The lithium-sulfur battery of claim 38, 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.

49. The lithium-sulfur battery of claim 38, wherein a packing density of the one or more porous carbon layers is at least 7 mg/cm².

50. The lithium-sulfur battery of claim 38, wherein a thickness of the one or more porous carbon layers is between about 10 pm and about 200 pm.

51. The lithium-sulfur battery of claim 38, wherein an average size of the porous primary carbon nanoparticles is between about 20 nm and about 50 nm.

52. The lithium-sulfur battery of claim 38, wherein the 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).

53. The lithium-sulfur battery of claim 38, wherein an average size of the porous carbon agglomerates is at least 1 pm.

54. The lithium-sulfur battery of claim 38, further including a separator disposed between the anode and the cathode.

55. The lithium-sulfur battery of claim 54, wherein the separator includes a microporous monolayer polypropylene membrane.

56. The lithium-sulfur battery of claim 54, wherein the separator includes a ceramics-coated material.

57. A lithium- sulfur battery including: a lithium- alloy anode; an anode protective coating disposed on the anode, wherein the anode protective coating includes an ionic liquid entrapped within a polymer matrix; a cathode; and a liquid fluorinated ether electrolyte including one or more of lithium nitrate (LiNOs) or lithium bis (trifluoromethanesulfonyl) (LiTFSI).

58. The lithium-sulfur battery of claim 57, wherein the anode includes a freestanding lithium-alloy anode.

59. The lithium-sulfur battery of claim 58, wherein the Li-alloy includes a 90 wt% Li- 10 wt% Mg alloy.

60. The lithium-sulfur battery of claim 57, wherein the polymer matrix includes one or more acrylate groups or ethylene oxide groups.

61. The lithium-sulfur battery of claim 57, wherein an amount of the ionic liquid entrapped in the polymer matrix is between about 10 wt% and about 40 wt%.

62. A roll-to-roll method of disposing one or more anode protective layers on an anode active material associated with a lithium-sulfur battery, the method including: arranging one or more anode active material layers and one or more alloying metal layers as feed material layers to a calender; passing the feed material layers through the calender, wherein each surface of the one or more anode active material layers is in contact with the one or more alloying metal layers in the calender; and forming in situ a reacted alloy layer on each surface of the anode active material layer during calendering, wherein the reacted alloy layer is a reaction product of the one or more anode active material layers reacting with the one or more alloying metal layers.

63. A method of disposing one or more protective layers on an anode active material associated with a lithium-sulfur battery, the method including: forming a reacted alloy layer on each surface of the anode active material using the method of claim 62; and depositing a polymer coating on the reacted alloy layer disposed on each surface of the anode active material.

64. The method of claim 63, wherein a thickness of the reacted alloy layer is less than 1 pm.

65. The method of claim 63, wherein the polymer coating includes one or more of poly vinylidene fluoride (PVDF), pentaerythritol tetraacrylate (PETEA), or polyethylene glycol dimethacrylate (PEGDMA).

66. The method of claim 63 wherein a thickness of the polymer coating is less than 1 pm.

67. A method of disposing an anode protective coating on an anode associated with a lithium sulfur battery, the method including: preparing a coating solution by mixing precursors including one or more monomers or oligomers, an ionic liquid, one or more lithium salts, and a polymerization initiator in a solvent; applying the coating solution to the anode; initiating the polymerization of the one or more monomers or oligomers; removing the solvent by drying; and forming a polymer matrix infused with the ionic liquid by curing the coating, wherein an amount of precursors in the coating solution is between about 3 wt% and about 30 wt%.

68. The method of claim 67, wherein a loading of the polymer matrix infused with ionic liquid on the anode is between about 10 pg/cm² and about 600 pg/cm².