172 Search Results

Polysulfides are poorly retained within porous cathodes and readily diffuse into the electrolyte over time, leading to the well-known shuttle effect that undermines the reversibility of Li-S batteries. Here, in this study, we demonstrate that catalytic disproportionation of polysulfides provides an effective pathway to suppress this process by rapidly converting dissolved species into solid sulfur and sulfides, thereby preventing their migration into the electrolyte. Fundamentally, the sluggish kinetics of sulfur redox reactions are responsible for the accumulation and redistribution of soluble polysulfides in the bulk electrolyte. By accelerating these kinetics, catalyzed disproportionation not only confines sulfur within the conductive cathodemore » matrix but also promotes the homogeneous precipitation of Li₂S₂/Li₂S, which enhances electrochemical reversibility and cycling stability. Using nitrogen-doped carbon (NC800) as a model catalyst, we reveal its ability to drive a pseudo-16-electron reduction pathway, leading to a single dominant Li₂S product and uniform deposition within the porous framework. In contrast, a non-catalytic carbon (KB) yields multiple polysulfide intermediates and heterogeneous deposition. The mechanistic insights provided here highlight the pivotal role of catalytic disproportionation in reshaping sulfur redox pathways and offer a rational strategy for mitigating polysulfide shuttling in practical Li-S pouch cells.« less

To mitigate the “polysulfide shuttle” in lithium–sulfur batteries, different hosting materials that can interact with the polysulfide species physically or chemically have been widely investigated. Copper sulfides as one type of material are believed to have strong chemical interactions with the polysulfide species to consequently influence the performances of Li–S batteries. In this work, high-performance liquid chromatography (HPLC), electrospray ionization mass spectrometry (ESI/MS), scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM-EDS), and inductively coupled plasma optical emission spectroscopy (ICP-OES) were used to systematically investigate the interactions between ether-based polysulfide solutions and copper sulfides (as well as silver sulfide). Furthermore, basedmore » on chromatographic and spectroscopic results, the interactions between polysulfides and Cu₂S can be classified into two types of reactions: one is the redox reaction with the formation of CuS, while another is the complexation reaction with the formation of soluble LiCuS_n (n ≥ 4). Contrarily, Ag₂S (and CuS) shows no interactions with polysulfides. Accordingly, the cycling behaviors of Li–S batteries with copper sulfides as hosting materials or with copper as additives were explained reasonably.« less

Sodium-ion batteries offer low-cost energy storage solutions for the grid and electric vehicles, leveraging the established "rocking-chair" Li-ion design and the natural abundance of sodium. However, SIBs face challenges such as relatively lower voltage and capacity than lithium-ion batteries, as well as dependence on nickel resources. Here, in this work, a new nickel-free cathode material, Na_0.75Li_0.08Cu_0.25Mn_0.66O₂, was designed and synthesized. This material has a capacity of ~125 mAh/g and an average discharge voltage of 3.5 V. Notably, more than one-third of the capacity arises from lithium substitution of Cu (~8 mol.%) and high voltage activation to 4.6 V. Multimodal synchrotronmore » x-ray characterization combining spectroscopy, microscopy, and scattering reveal the capacity is primarily from the redox of copper and oxygen, with a minor contribution from the manganese redox. Lithium substitution alters the phase transition mechanism from a two-phase transition in P3-Na_2/3Cu_1/3Mn_2/3O₂ to a solid-solution in Na_0.75Li_0.08Cu_0.25Mn_0.66O₂, enhancing the reversibility of this material.« less

Abundant sodium (Na) batteries are a sustainable alternative to resource-constrained lithium-ion batteries, offering huge cost advantages. However, developing high-voltage anode-free sodium metal batteries (SMBs) to narrow the energy density gap with lithium-ion batteries is hindered by a critical challenge: existing electrolytes cannot simultaneously achieve ultra-high Na coulombic efficiency and anodic stability. Here, in this study, we present a rationally designed non-fluorinated electrolyte (1.0 M NaPF₆ in 1,2-diethoxyethane/1,2-di-tert-butoxyethane) to address this key limitation, achieving Na coulombic efficiency of >99.95% and anodic stability of >4.8 V. For coin cells (2.0 mAh cm⁻², N/P = 1.7), our electrolyte design enables 4.0 V Namore » | |Na₃V₂(PO₄)₃ (NVP) at 5 C and 4.3 V Na | |NaNi_0.6Mn_0.2Co_0.2O₂ (NMC622) at 0.3 C for 5,000 and 500 cycles with a capacity retention >80%. Remarkably, the 50 mAh anode-free pouch cells 4.0 V Al | |NVP and 4.3 V Al | |NMC622 also achieve 500 and 300 cycles (retention >75%) with a specific energy of >360 Wh kg_(electrode)⁻¹. This work focuses on electrolyte optimization and conceptual advances, whereas critical aspects such as safety, large-scale manufacturability and practical feasibility of SMBs require further investigation. The electrolyte design using non-fluorinated solvents enhances the anodic stability without sacrificing Na efficiency, laying groundwork for advancing low-cost, high-energy SMBs and supporting the transition to sustainable battery technologies.« less

Anion-derived interphases are crucial for extending the cycle life of lithium metal batteries. While their benefits are often attributed to crystalline inorganic species like LiF and Li₂O, the role of amorphous inorganic species and the interplay between the anode-electrolyte interphase (SEI) and the cathode-electrolyte interphase (CEI) remain largely unexplored. Here, in this study, we examine two model electrolyte systems─one with solvent-derived interphases and the other with anion-derived interphases─using advanced X-ray scattering and spectroscopy techniques. Our findings reveal that anion-derived interphases contain substantial amounts of amorphous inorganic species, leading to a unique synchronization of "breathing" between SEI and CEI. During charging,more » the SEI grows while the CEI shrinks; during discharging, these roles reverse. This distinctive interfacial behavior originates from the competition of deposition and dissolution of amorphous inorganics during cycling. The study highlights the unique role of amorphous inorganics in anion-derived interphases, providing new insights into improving battery performance and durability.« less

The use of aqueous/non-aqueous biphasic electrolyte solutions in Li-based battery systems circumvents the limitations of poor reductive stability of aqueous electrolyte solutions, broadening their electrochemical stability window. However, aqueous/non-aqueous electrolytes suffer from biphasic mixing and high impedance when Li ions cross the biphasic interface. Here we propose the use of 12-crown-4 (12C4) and tetraglyme (G4) as lithium ionophores to form Li⁺(ionophore) nanoclusters in both non-aqueous and aqueous phases to overcome the interface challenges in biphasic electrolytes. The Li⁺(ionophore) nanoclusters have the H₂O-excluding inner Li⁺ solvation structure in non-polar 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), allowing fast charge transport across the biphasic interfacemore » without solvent mixing or water shuttling. Further, a tailored electrolyte formulation comprising the lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt, 12C4, TTE and H₂O solvents (labelled LiTFSI-12C4@TTE/H₂O) demonstrates low impedance (2.7 Ω cm^-2) at the TTE/H₂O interface and enabling 2,000 cycles of prelithiated graphite||LiFePO₄ coin cells at 850 mA g^-1 with an average Coulombic efficiency of 99.8%. Single-layer 22.5 mAh Li||LiMn₂O₄ pouch cells using LiTFSI-12C4@TTE/H₂O electrolyte with G4 delivered a stable discharge capacity of about 1.3 mAh cm^-2 for 80 cycles at 0.5 mA cm^-2.« less

A novel high-donor 3-fluoropyridine (3FPy) electrolyte has been introduced for use in Li-S batteries, demonstrating an inhibition effect on the polysulfide shuttle, even without the addition of LiNO₃. In this study, fluoropyridine electrolytes, including 2-fluoropyridine (2FPy) and 3FPy electrolytes, are studied using electrochemical analysis, mass spectrometry (MS), and high-performance liquid chromatography (HPLC) methods. Collision-induced dissociation spectra revealed that Li⁺ preferentially solvates with different fluoropyridines, with 2FPy exhibiting a stronger interaction due to ortho-fluorine's influence, compared to 4FPy and 3FPy. However, MS and HPLC analyses showed that 2FPy is reactive with polysulfides, while 3FPy offers high solubility for polysulfides and sulfurmore » without reacting with them at room temperature. Further, despite 3FPy performing well at room temperature, further electrochemistry studies at elevated (60 °C) and reduced (0 °C) temperatures reveal the challenges. At high temperatures, LiNO₃ is essential to suppress the polysulfide shuttle; and at low temperatures, the performance with the 3FPy electrolyte significantly lags behind that of the ether-based electrolyte.« less

Hydrogen oxidation reaction in alkaline media is critical for alkaline fuel cells and electrochemical ammonia compressors. The slow hydrogen oxidation reaction in alkaline electrolytes requires large amounts of scarce and expensive platinum catalysts. While transition metal decoration can enhance Pt catalysts’ activity, it often reduces the electrochemical active surface area, limiting the improvement in Pt mass activity. Here, we enhance Pt catalysts’ activity without losing surface-active sites by using a Pd-Ru pair. Utilizing a mildly catalytic thermal pyrolysis approach, Pd-Ru pairs are decorated on Pt, confirmed by extended X-ray absorption fine structure and high-angle annular dark-field scanning transmission electron microscopy.more » Density functional theory and ab-initio molecular dynamics simulations indicate preferred Pd and Ru dopant adsorption. The Pd-Ru decorated Pt catalyst exhibits a mass-based exchange current density of 1557 ± 85 A g^–1_metal for hydrogen oxidation reaction, demonstrating superior performance in an ammonia compressor.« less

Abstract Micro-sized silicon anodes can significantly increase the energy density of lithium-ion batteries with low cost. However, the large silicon volume changes during cycling cause cracks for both organic-inorganic interphases and silicon particles. The liquid electrolytes further penetrate the cracked silicon particles and reform the interphases, resulting in huge electrode swelling and quick capacity decay. Here we resolve these challenges by designing a high-voltage electrolyte that forms silicon-phobic interphases with weak bonding to lithium-silicon alloys. The designed electrolyte enables micro-sized silicon anodes (5 µm, 4.1 mAh cm ⁻² ) to achieve a Coulombic efficiency of 99.8% and capacity of 2175 mAh gmore » ⁻¹ for >250 cycles and enable 100 mAh LiNi _0.8 Co _0.15 Al _0.05 O ₂ pouch full cells to deliver a high capacity of 172 mAh g ⁻¹ for 120 cycles with Coulombic efficiency of >99.9%. The high-voltage electrolytes that are capable of forming silicon-phobic interphases pave new ways for the commercialization of lithium-ion batteries using micro-sized silicon anodes.« less

Abstract Li metal batteries using Li metal as negative electrode and LiNi _1-x-y Mn _x Co _y O ₂ as positive electrode represent the next generation high-energy batteries. A major challenge facing these batteries is finding electrolytes capable of forming good interphases. Conventionally, electrolyte is fluorinated to generate anion-derived LiF-rich interphases. However, their low ionic conductivities forbid fast-charging. Here, we use CsNO ₃ as a dual-functional additive to form stable interphases on both electrodes. Such strategy allows the use of 1,2-dimethoxyethane as the single solvent, promising superior ion transport and fast charging. LiNi _1-x-y Mn _x Co _y O ₂more » is protected by the nitrate-derived species. On the Li metal side, large Cs ⁺ has weak interactions with the solvent, leading to presence of anions in the solvation sheath and an anion-derived interphase. The interphase is surprisingly dominated by cesium bis(fluorosulfonyl)imide, a component not reported before. Its presence suggests that Cs ⁺ is doing more than just electrostatic shielding as commonly believed. The interphase is free of LiF but still promises high performance as cells with high LiNi _0.8 Mn _0.1 Co _0.1 O ₂ loading (21 mg/cm ² ) and low N/P ratio (~2) can be cycled at 2C (~8 mA/cm ² ) with above 80% capacity retention after 200 cycles. These results suggest the role of LiF and Cs-containing additives need to be revisited.« less