148 Search Results

Increasing the energy density of batteries can accelerate the deployment of electric vehicles, expand the utilization of renewable energy and, in turn, reduce greenhouse gas emissions. Different from commercially available lithium-ion batteries, high-energy-density lithium-metal batteries use metallic lithium instead of graphite as the negative electrode. Furthermore, the commercialization of lithium-metal batteries is hindered by the electrochemical instability of lithium metal. Polymer coatings have shown promise in addressing issues related to each step of heterogeneous lithium deposition. Here we summarize the current understanding of key design principles and highlight relevant coating compositions. Moreover, we discuss high-performing coating–electrolyte pairs and provide anmore » outlook on interface design for novel electrolytes.« 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

An emerging design heuristic for electrochemical nitrate reduction (NO₃RR) catalysts is synthesizing electron-deficient sites to facilitate binding of electron-rich NO₃^–. However, this rule has rarely been applied to metal-, nitrogen-doped carbon (MNC) catalysts. Titanium (Ti), with low electronegativity and high NO₃RR reactivity, is a compelling MNC candidate. To date, atomically dispersed TiN_x motifs have eluded synthesis due to the strong oxophilicity of Ti. Here, in this work, we leverage nitrogen-rich carbon flowers (CF) to overcome synthetic challenges and produce Ti-, N-doped carbon flower (TiCF) catalysts. Advanced materials characterization demonstrates that TiCF catalysts are a mixed phase material with 3/4 ofmore » Ti atoms in TiO₂-like nanoparticles and 1/4 of Ti atoms in novel, atomically dispersed TiN_x sites. TiCF achieves 61 ± 7% NH₃-selectivity at −0.70 V vs RHE and 14 ± 5 mA/cm² to NH₃ formation (|j_NH3|) at −0.85 V vs RHE in (0.1 M NaOH + 0.1 M NaNO₃ + 0.45 M Na₂SO₄) electrolyte. Control studies show both CF morphology and Ti sites are essential for high NO₃RR activity. Density functional theory calculations attribute the NO3RR reactivity to TiN_x, which facilitates multiple bond formation with surface intermediates to promote favorable NH3 synthesis pathways. Thus, TiCF exhibits 60× higher |j_NH3| values than bulk Ti and NH₃ yield rates (>0.06 mmol NH₃/h/cm²) that are competitive with state-of-the-art MNC catalysts (e.g., FeNC, CuNC). TiCF introduces a new class of Ti electrocatalysts, advancing the MNC design space and sustainable NH₃ production.« less

The electrolyte plays a critical role in lithium metal batteries. In particular, ion solvation profoundly impacts key electrolyte properties and battery performance. Here, in this study, we systematically investigate solvation-property relationships in a series of electrolytes with different solvent-diluent ratios. Through potentiometric techniques that measure the relative solvation free energies of electrolytes, we find that weaker solvation correlates with larger ion clusters, lower ionic conductivity and diffusion coefficient, and superior electrochemical stability. Weaker solvation leads to the formation of a small number of Li clusters with large hydrodynamic radii, which lowers the Li⁺ diffusivity and ionic conductivity of the electrolyte.more » Concurrently, weaker solvation leads to improved electrochemical stability at both the cathode and anode interfaces. Understanding these solvation-property relationships and trade-offs is important to designing electrolytes for optimized lithium metal battery performance.« less

Perfluoroalkyls (PFAS) continue to emerge as a global health threat making their effective detection and capture extremely important. Though metal–organic frameworks (MOFs) have stood out as a promising class of porous materials for sensing PFAS, detection limits remain insufficient and a fundamental understanding of detection mechanisms warrants further investigation. Here, in this study, we show the use of a 2D conductive MOF film based on copper hexahydroxy triphenylene (Cu-HHTP) to fabricate chemiresistive sensing devices for detecting PFAS in drinking water. We further show ultrasensitive detection using electrochemical impedance spectroscopy. Owing to excellent electrostatic attractions and electrochemical interactions between the copper-basedmore » MOF and PFAS, confirmed by high-resolution spectroscopy and theoretical simulations, the MOF-based sensor reported herein exhibits excellent affinity and sensitivity toward perfluorinated acids at concentrations as low as 0.002 ng/L.« less

Recent electrolyte solvent design based on weakening lithium-ion solvation have shown promise in enhancing cycling performance of Li-metal batteries. However, they often face slow redox kinetics and poor cycling reversibility at high rate. Here we report using asymmetric solvent molecules substantially accelerates Li redox kinetics. Asymmetric ethers (1-ethoxy-2-methoxyethane, 1-methoxy-2-propoxyethane) showed higher exchange current densities and enhanced high-rate Li⁰ plating/stripping reversibility compared to symmetric ethers. Adjusting fluorination levels further improved oxidative stability and Li⁰ reversibility. The asymmetric 1-(2,2,2-trifluoro)-ethoxy-2-methoxyethane, with 2 M lithium bis(fluorosulfonyl)imide, exhibited high exchange current density, oxidative stability, compact solid–electrolyte interphase (~10 nm). This electrolyte exhibited superior performance among state-of-the-art electrolytes,more » enabling over 220 cycles in high-rate Li (50 μm)||LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811, 4.9 mAh cm⁻²) cells and for the first time over 600 cycles in anode-free Cu | |Ni95 pouch cells (200 mAh) under electric vertical take-off and landing cycling protocols. Our findings on asymmetric molecular design strategy points to a new pathway towards achieving fast redox kinetics for high-power Li-metal batteries.« less

High degree of fluorination for ether electrolytes has resulted in improved cycling stability of lithium metal batteries due to stable solid electrolyte interphase (SEI) formation and good oxidative stability. However, the sluggish ion transport and environmental concerns of high fluorination degree drive the need to develop less fluorinated structures. Here, we depart from the traditional ether backbone and introduce bis(2-fluoroethoxy)methane (F2DEM), featuring monofluorination of the acetal backbone. High coulombic efficiency and stable long-term cycling in Li||Cu half cells can be achieved with F2DEM even under fast Li metal plating conditions. The performance of F2DEM is further compared with diethoxymethane (DEM)more » and 2-[2-(2,2-difluoroethoxy)ethoxy]-1,1,1-trifluoroethane (F5DEE). A significantly lower overpotential is observed with F2DEM, which improves energy efficiency and enables its application in high-rate conditions. Comparative studies of F2DEM with DEM and F5DEE in anode-free lithium iron phosphate (LiFePO4) LFP pouch cells and high-loading LFP coin cells further show improved capacity retention of F2DEM electrolyte, demonstrating its practical applicability. More importantly, we also extensively investigate the underlying mechanism for the superior performance of F2DEM through various techniques, including X-ray photoelectron spectroscopy, scanning electron microscopy, cryogenic electron microscopy, focused ion beam, electrochemical impedance spectroscopy, and titration gas chromatography. Overall, F2DEM facilitates improved Li deposition morphology with reduced amount of dead Li. This enables F2DEM to show superior performance, especially under higher charging and slower discharging rate conditions.« less

The performance of all‐polymer solar cells is often enhanced by incorporating solvent additives during solution processing. Here, in particular, blends based on the model all‐polymer system PBDBT:N2200 have been shown to have increased short‐circuit current and fill factor when processed with dilute diiodooctane (DIO). However, the morphological mechanism that drives the increase in performance is often not well understood due to limitations in common characterization techniques. In this study, it is shown that a combination of X‐ray techniques with cryogenic high‐resolution transmission electron microscopy (HRTEM) analysis can provide a quantitative and spatially resolved picture of polymer chain orientation and alignmentmore » in all‐polymer blends. It is found that DIO induces vertical phase separation in PBDBT‐2F:F‐N2200 and increases donor crystallite thickness in the pi‐stacking direction leading to an acceptor‐rich film surface. However, it is also shown that DIO does not disrupt the formation of face‐on donor–acceptor interfaces. These findings suggest that dilute DIO primarily affects crystalline domain formation in single component regions as opposed to mixed regions; thus, dilute DIO can impact vertical charge transport pathways without sacrificing donor–acceptor interfacial connectivity.« less

Tuning the solvation structure of lithium ions via electrolyte engineering has proven effective for lithium metal (Li) anodes. Further advancement that bypasses the trial-and-error practice relies on the establishment of molecular design principles. Expanding the scope of our previous work on solvent fluorination, we report here an alternative design principle for non-fluorinated solvents, which potentially have reduced cost, environmental impact, and toxicity. By studying non-fluorinated ethers systematically, we found that the short-chain acetals favor the [gauche, gauche] molecular conformation due to hyperconjugation, which leads to weakened monodentate coordination with Li⁺. The dimethoxymethane electrolyte showed fast activation to >99% coulombic efficiencymore » (CE) and high ionic conductivity of 8.03 mS cm^-1. The electrolyte performance was demonstrated in anode-free Cu$$∥$$LFP pouch cells at current densities up to 4 mA cm^-2 (70 to 100 cycles) and thin-Li$$∥$$high-loading-LFP coin cells (200–300 cycles). Overall, we demonstrated and rationalized the improvement in Li metal cyclability by the acetal structure compared to ethylene glycol ethers. We expect further improvement in performance by tuning the acetal structure.« less

Lithium bis(fluorosulfonyl)imide-based liquid electrolytes are promising for realizing high Coulombic efficiency and long cycle life for next-generation Li-metal batteries. However, the role of anions in the formation of solid-electrolyte interphase remains unclear. Herein, we combine electrochemical analyses and X-ray photoelectron spectroscopy measurements both with and without sample washing, together with computational simulations, to propose the reaction pathways of electrolyte decomposition and correlate the interphase component solubility with the efficacy of passivation. Additionally, we discovered that not all the products derived from interphase-forming reactions were incorporated into the resulting passivation layer, with a notable portion present in the liquid electrolyte. Further,more » we found that the high-performance electrolytes can afford a sufficiently passivating interphase with minimized electrolyte decomposition, by incorporating more anion-decomposition products. Overall, this work presents a systematic approach of coupling electrochemical and surface analyses to paint a comprehensive picture of solid-electrolyte interphase formation, while identifying key attributes of high-performance electrolytes for guiding future designs.« less