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The interrelation is explored between external pressure (0.1, 1, and 10 MPa), solid electrolyte interphase (SEI) structure/morphology, and lithium metal plating/stripping behavior. To simulate anode‐free lithium metal batteries (AF‐LMBs) analysis is performed on “empty” Cu current collectors in standard carbonate electrolyte. Lower pressure promotes organic‐rich SEI and macroscopically heterogeneous, filament‐like Li electrodeposits interspersed with pores. Higher pressure promotes inorganic F‐rich SEI with more uniform and denser Li film. A “seeding layer” of lithiated pristine graphene (pG@Cu) favors an anion‐derived F‐rich SEI and promotes uniform metal electrodeposition, enabling extended electrochemical stability at a lower pressure. State‐of‐the‐art electrochemical performance is achieved at 1MPa: pG‐enabled half‐cell is stable after 300 h (50 cycles) at 1 mA cm⁻²rate −3 mAh cm⁻²capacity (17.5 µm plated/stripped), with cycling Coulombic efficiency (CE) of 99.8%. AF‐LMB cells with high mass loading NMC622 cathode (21 mg cm⁻²) undergo 200 cycles with a CE of 99.4% at C/5‐charge and C/2‐discharge (1C = 178 mAh g⁻¹). Density functional theory (DFT) highlights the differences in the adsorption energy of solvated‐Li⁺onto various crystal planes of Cu (100), (110), and (111), versus lithiated/delithiated (0001) graphene, giving insight regarding the role of support surface energetics in promoting SEI heterogeneity.

 

In this work, the Na–K liquid alloy with a charge selective interfacial layer is developed to achieve an impressively long cycling life with small overpotential on a sodium super‐ionic conductor solid‐state electrolyte (NASICON SSE). With this unique multi‐cation system as the platform, we further propose a unique model that contains a chemical decomposition domain and a kinetic decomposition domain for the interfacial stability model. Based on this model, two charge selection mechanisms are proposed with dynamic chemical kinetic equilibrium and electrochemical kinetics as the manners of control, respectively, and both are validated by the electrochemical measurements with microscopic and spectroscopic characterizations. This study provides an effective design for high‐energy‐density solid‐state battery with alkali Na–K anode, but also presents a novel approach to understand the interfacial chemical processes that could inspire and guide future designs.

 

This is the first report of molybdenum carbide‐based electrocatalyst for sulfur‐based sodium‐metal batteries. MoC/Mo₂C is in situ grown on nitrogen‐doped carbon nanotubes in parallel with formation of extensive nanoporosity. Sulfur impregnation (50 wt% S) results in unique triphasic architecture termed molybdenum carbide–porous carbon nanotubes host (MoC/Mo₂C@PCNT–S). Quasi‐solid‐state phase transformation to Na₂S is promoted in carbonate electrolyte, with in situ time‐resolved Raman, X‐ray photoelectron spectroscopy, and optical analyses demonstrating minimal soluble polysulfides. MoC/Mo₂C@PCNT–S cathodes deliver among the most promising rate performance characteristics in the literature, achieving 987 mAh g⁻¹at 1 A g⁻¹, 818 mAh g⁻¹at 3 A g⁻¹, and 621 mAh g⁻¹at 5 A g⁻¹. The cells deliver superior cycling stability, retaining 650 mAh g⁻¹after 1000 cycles at 1.5 A g⁻¹, corresponding to 0.028% capacity decay per cycle. High mass loading cathodes (64 wt% S, 12.7 mg cm⁻²) also show cycling stability. Density functional theory demonstrates that formation energy of Na₂S_x(1 ≤x ≤ 4) on surface of MoC/Mo₂C is significantly lowered compared to analogous redox in liquid. Strong binding of Na₂S_x(1 ≤x ≤ 4) on MoC/Mo₂C surfaces results from charge transfer between the sulfur and Mo sites on carbides’ surface.

 

Repeated cold rolling and folding is employed to fabricate a metallurgical composite of sodium–antimony–telluride Na₂(Sb_2/6Te_3/6Vac_1/6) dispersed in electrochemically active sodium metal, termed “NST‐Na.” This new intermetallic has a vacancy‐rich thermodynamically stable face‐centered‐cubic structure and enables state‐of‐the‐art electrochemical performance in widely employed carbonate and ether electrolytes. NST‐Na achieves 100% depth‐of‐discharge (DOD) in 1mNaPF₆in G2, with 15 mAh cm⁻²at 1 mA cm⁻²and Coulombic efficiency (CE) of 99.4%, for 1000 h of plating/stripping. Sodium‐metal batteries (SMBs) with NST‐Na and Na₃V₂(PO₄)₃ (NVP) or sulfur cathodes give significantly improved energy, cycling, and CE (>99%). An anode‐free battery with NST collector and NVP obtains 0.23% capacity decay per cycle. Imaging and tomography using conventional and cryogenic microscopy (Cryo‐EM) indicate that the sodium metal fills the open space inside the self‐supporting sodiophilic NST skeleton, resulting in dense (pore‐free and solid electrolyte interphase (SEI)‐free) metal deposits with flat surfaces. The baseline Na deposit consists of filament‐like dendrites and “dead metal”, intermixed with pores and SEI. Density functional theory calculations show that the uniqueness of NST lies in the thermodynamic stability of the Na atoms (rather than clusters) on its surface that leads to planar wetting, and in its own stability that prevents decomposition during cycling.

 

Graphite anodes offer low volumetric capacity in lithium‐ion batteries. By contrast, tellurene is expected to alloy with alkali metals with high volumetric capacity (≈2620 mAh cm⁻³), but to date there is no detailed study on its alloying behavior. In this work, the alloying response of a range of alkali metals (A = Li, Na, or K) with few‐layer Te is investigated. In situ transmission electron microscopy and density functional theory both indicate that Te alloys with alkali metals forming A₂Te. However, the crystalline order of alloyed products varies significantly from single‐crystal (for Li₂Te) to polycrystalline (for Na₂Te and K₂Te). Typical alloying materials lose their crystallinity when reacted with Li—the ability of Te to retain its crystallinity is therefore surprising. Simulations reveal that compared to Na or K, the migration of Li is highly “isotropic” in Te, enabling its crystallinity to be preserved. Such isotropic Li transport is made possible by Te's peculiar structure comprising chiral‐chains bound by van der Waals forces. While alloying with Na and K show poor performance, with Li, Te exhibits a stable volumetric capacity of ≈700 mAh cm⁻³, which is about twice the practical capacity of commercial graphite.

 

A stable lean‐electrolyte operating lithium–sulfur (Li–S) battery based on a cathode of Li₂S in situ electrocatalytically deposited from L₂S₈catholyte onto a support of metallic molybdenum disulfide (1T‐MoS₂) on carbon cloth (CC) is created. The 1T‐MoS₂significantly accelerates the conversion Li₂S₈catholyte to Li₂S, chemically adsorbs lithium polysulfide (LiPSs) from solution, and suppresses crossover of the LiPSs to the anode. These experimental findings are explained by density functional theory calculations that show that 1T‐MoS₂gives rise to strong adsorption of polysulfides on its surface and is electrocatalytic for the targeted reversible Li–S conversion reactions. The CC/1T‐MoS₂electrode in a Li–S battery delivers an initial capacity of 1238 mAh g⁻¹, with a low capacity fade of only 0.051% per cycle over 500 cycles at 0.5C. Even at a high sulfur loading (4.4 mg cm⁻²) and low electrolyte/S (E/S) ratio of 3.7 µL mg⁻¹, the battery achieves an initial reversible capacity of 1176 mA h g⁻¹at 0.5C, with 87% capacity retention after 160 cycles. The post 500 cycles Li metal opposing 1T‐MoS₂is substantially smoother than the Li opposing CC, with XPS supporting the role of 1T‐MoS₂in inhibiting LiPSs crossover.

 

Sodium metal battery (SMB, NMB) anodes can become dendritic due to an electrochemically unstable native Na-based solid electrolyte interphase (SEI). Herein Li-ion activated tin sulfide graphene nanocomposite membrane (A-SnS–G) is employed as an artificial SEI layer, allowing cyclability of record-thin 100 μm Na metal foils. The thin Na metal is prepared by a self-designed metallurgical rolling protocol. A-SnS–G is initially placed onto the polypropylene (PP) separator but becomes in situ transferred onto the Na metal surface. Symmetric metal cells protected by A-SnS–G achieve low-overpotential extended high-rate cycling in a standard carbonate electrolyte (EC : DEC = 1 : 1, 5% FEC). Accumulated capacity of 1000 mA h cm −2 is obtained after 500 cycles at 4 mA cm −2 , with accumulated capacity-to-foil capacity (A/F) ratio of 90.9. This is among the most favorable cycle life, accumulated capacity, and anode utilization combinations reported. Protection by non-activated SnS–G membrane yields significantly worse cycling, albeit still superior to the baseline unprotected sodium. Post-mortem and dedicated light optical analysis indicate that metal swelling, dendrite growth and dead metal formation is extensive for the unprotected sample, but is suppressed with A-SnS–G. Per XPS, post-100 cycles near-surface structure of A-SnS–G is rich in metallic Sn alloys and inorganic carbonate salts. Even after 300 cycles, Li-based SEI components ROCO 2 -Li, Li 2 CO 3 and LiF are detected with A-SnS–G. As a proof of principle, an SMB with a high mass loading (6 mg cm −2 ) NVP cathode and a A-SnS–G protected anode delivered extended cyclability, achieving 74 mA h g −1 after 400 cycles at 0.4C.