11 research outputs found
Numerical and experimental investigations of mass transport in proton exchange membrane fuel cells
No full text
In Situ Growth of 2D Metal–Organic Framework Ion Sieve Interphase for Reversible Zinc Anodes
No full textZinc metal anodes are gaining popularity in aqueous electrochemical energy storage systems for their high safety, cost-effectiveness, and high capacity. However, the service life of zinc metal anodes is severely constrained by critical challenges, including dendrites, water-induced hydrogen evolution, and passivation. In this study, a protective two-dimensional metal–organic framework interphase is in situ constructed on the zinc anode surface with a novel gel vapor deposition method. The ultrathin interphase layer (~1 μm) is made of layer-stacking 2D nanosheets with angstrom-level pores of around 2.1 Å, which serves as an ion sieve to reject large solvent–ion pairs while homogenizes the transport of partially desolvated zinc ions, contributing to a uniform and highly reversible zinc deposition. With the shielding of the interphase layer, an ultra-stable zinc plating/stripping is achieved in symmetric cells with cycling over 1000 h at 0.5 mA cm−2 and ~700 h at 1 mA cm−2, far exceeding that of the bare zinc anodes (250 and 70 h). Furthermore, as a proof-of-concept demonstration, the full cell paired with MnO2 cathode demonstrates improved rate performances and stable cycling (1200 cycles at 1 A g−1). This work provides fresh insights into interphase design to promote the performance of zinc metal anodes.</p
Quadrilateral-Patterned Perforated Gas Diffusion Layers Boost the Performance of Fuel Cells
No full textWater flooding remains a critical challenge that hinders
the operation
of fuel cells at high current and power densities. Here, we develop
a novel gas diffusion layer (GDL) featuring quadrilaterally patterned
perforations to boost the water drainage capability in proton exchange
membrane fuel cells. When the perforations are vertically arranged
to flow channels, the fuel cell can achieve a peak power density of
1.43 W cm–2 and a current density of as high as
5400 mA cm–2, far outperforming those with commercial
GDLs with and without a microporous layer by 28.6% and 58.8%, respectively.
Pore-scale simulations reveal that the patterned perforations reduce
the breakthrough pressure and facilitate water removal, thus improving
oxygen diffusion in the perforated GDLs, while cell-scale simulations
show that the vertically arranged perforations to flow channels significantly
enhance water removal to the adjacent channels due to the improved
in-plane permeability, thereby reducing liquid water saturation and
boosting cell performance
Quadrilateral-patterned perforated gas diffusion layers boost the performance of fuel cells
No full text202405 bcrcAccepted ManuscriptRGCPublishedGreen (AAM
Engineering Molecule-Designed In Situ Polymerization on Al-Doped Molecular-Sieve Framework Enables Robust Quasi-Solid-State Lithium Batteries
No full textAchieving fast Li+ transport kinetics and stable electrode/electrolyte interfaces is of paramount importance, yet extremely challenging for the practical success of solid-state lithium metal batteries, which requires the rational design of the structure and composition of solid-state electrolytes. Herein, a composite quasi-solid-state electrolyte is fabricated through in situ polymerization of a molecule-designed polymer chain within the functionalized molecular sieve framework (Al-MCM41). In this design, the robust Brønsted/Lewis acid–base interactions between Al-MCM41 and TFSI− facilitate the dissociation of lithium salt, leading to a Li+ transference number as high as 0.81. Meanwhile, the well-ordered mesopores of Al-MCM41 act as the “reservoir” of the polymer chain, creating continuous ionic migration pathways to offer an excellent Li+ conductivity of 1.09 × 10−3 S cm−1 at 30 °C. Furthermore, the polymer with fluorinated and nitrided functional groups guarantees a dual-reinforced anode and cathode interface. Such an integrated electrolyte with simultaneous unimpeded Li+ transport and robust interfaces delivers extraordinary capacity retention of 84.6% over 600 cycles at 5 C when coupled with LiFePO4 cathode and remarkable reversible capacity of 129.0 mAh g−1 after 200 cycles with high-voltage NCM622 cathode. This work provides a significant avenue for enhancing the practical feasibility of solid-state lithium metal batteries.</p
Developing Quasi-Solid-State Ether-Based Electrolytes with Trifluorotoluylation Ionic Liquids for High Voltage Lithium Metal Batteries
No full textThe practical application of quasi-solid-state ether-based electrolytes is hindered by lithium dendrite formation and poor oxidation stability, which reduce the cycle life and energy density of the battery. Here, taking advantage of the ionic liquids’ high ionic interactions and structural flexibility in forming an optimized electrode/electrolyte interface, a pyrrolidinium-based ionic liquids with trifluorotoluylation cationic segment is designed and developed. The oxidation of anions in the electrolytes is induced to form a robust inorganic LiF-rich interphase at the cathode, thereby effectively achieving high oxidation stability and suppressing the dissolution of transition metal ions. In addition, the LiF interphases derived from the trifluorotoluylation cations increase the modulus of the anode interface and suppress the growth of lithium dendrites. Therefore, the Li-LiFePO4, Li-LiCoO2, and Li-LiNi0.8Co0.1Mn0.1O2 full cells with the optimized electrolytes demonstrate remarkable performance improvements at high current density (10 C), a wide voltage range of 4.5 V, a high mass loading of 11.1 mg cm−2, and a wide temperature range of −20–80 °C. Furthermore, a 2.66 Ah-level pouch cell with a high-energy-density of exceeding 356 Wh kg‒1 and excellent cyclic stability demonstrates the potential of the strategy in providing a path for the practical application of quasi-solid-state ether-based electrolytes in high-energy-density batteries.</p
Engineering d-p Orbital Hybridization in a Single-Atom-Based Solid-State Electrolyte for Lithium-Metal Batteries
No full textRegulating lithium salt dissociation kinetics by enhancing the interaction between inorganic fillers and lithium salts is vital for enhancing the ionic conductivity in solid-state composite polymer electrolytes (CPEs). However, the influence of fillers’ external electronic environments on lithium salt dissociation dynamics remains unclear. Here, we design single-atom sites in metal–organic framework fillers for poly(ethylene oxide) (PEO)-based CPEs, boosting lithium salt dissociation through an electrocatalytic strategy. This strategy enhances lithium-ion conductivity by tuning the coupling strength between the d and p orbitals of the fillers, as captured by a newly identified descriptor (λ) via high-throughput density functional theory (DFT) calculations and machine learning. The optimal single atom (Ti) sites are incorporated into a ZIF-8 matrix for PEO-based CPEs, achieving an ionic conductivity exceeding 10−3 S cm−1 at 30 °C. Additionally, the electrolyte forms a robust solid electrolyte interphase and is compatible with LiCoO2, LiNi0.9Co0.05Mn0.05O2, and sulfur cathodes. Consequently, the solid-state lithium metal battery with the electrolyte demonstrates excellent cycling stability, maintaining performance over 5000 cycles at 10 C with LiFePO4 cathodes and stable operation at −30 °C. These findings highlight the transformative potential of engineering d-p orbital hybridization by incorporating single-atom sites into inorganic fillers for designing highly ion-conductive CPEs.</p
Efficacy and safety of dolutegravir plus lamivudine for patients with late presentation of HIV-1 infection: a retrospective real-world cohort study in Southwest China
No full textBackgroundEvidence regarding the use of dolutegravir plus lamivudine (DTG + 3TC) among patients with HIV infection who present late remains limited. This study aimed to evaluate the effectiveness and safety of DTG + 3TC therapy in patients with late presentation in Southwest China.MethodsThis single-center, retrospective cohort study included patients with late presentation who initiated DTG + 3TC anti-retroviral therapy (ART) between January 2020 and July 2023 (N = 176). Changes in immunologic and metabolic parameters as well as liver and kidney function, were assessed. The primary endpoint was the proportion of participants with HIV-1 RNA < 50 copies/mL at week 48. Late presentation was defined as CD4 < 350 cells/μL or the presence of AIDS-defining conditions.ResultsAt weeks 24 and 48, 83.0% (146/176) and 90.9% (160/176) of the patients achieved HIV-1 RNA levels <50 copies/mL, respectively. At week 48, the median CD4 count increased by 139.5 cells/μL (120.5–158.5), and the CD4/CD8 ratio increased by 0.2 (0.1–0.3) (p < 0.001). No patient discontinued treatment owing to adverse events during the observation period.ConclusionDTG + 3TC demonstrated high virologic efficacy and good tolerability in patients with late presentation. However, the regimen may be associated with an increase in lipid levels and weight, highlighting the need for regular monitoring
Upgrading Ion Migration and Interface Chemistry via a Cyano-Containing COF in a Single-Ion Conductive Polymer toward High-Voltage Lithium-Metal Batteries
No full textConcentration polarization-triggered dendrite growth hinders the practical application of solid-state polymer lithium batteries, which is caused by the uncontrolled anion migration in conventional dual-ion electrolytes. Single-ion conductive polymer electrolytes (SICPEs) offer a promise to mitigate dendrite growth via reducing concentration polarization and prohibiting salt depletion, yet they are highly challenging for successful implementation due to their narrow electrochemical window and poor ionic conductivity, which result from the deficient dissociation of Li+ polyanions and sluggish chain relaxation. Here, a cyano-containing covalent organic framework (COF) is designed to fuse with SICPEs, promising fast Li+ transport and remarkable interfacial stability toward high-voltage lithium-metal batteries. The electron-withdrawing cyano group on the COF facilitates the dissociation of the polyanions via ion-dipole interactions, resulting in more free-moving Li+. Rapid ion migration then occurs along the long-range cooperative ion transport pathways between the COF and SICPE. Additionally, the cyano group robustly bonds with transition metal ions of NCM cathodes to inhibit the catalytic decomposition of SICPE and guarantee the structural integrity of NCM. Hence, the as-prepared SICPE exhibits a significantly enhanced ionic conductivity of 9.2 × 10-4 S cm-1 and an improved Li+ transference number of 0.94 at room temperature. Accordingly, the NCM622\\Li quasi-solid-state cell achieves an exceptional capacity retention of 92.0% over 1000 cycles at 0.5 C, while the cell pairing with the 4.8 V NCM622 cathode delivers a remarkable capacity of 149.5 mAh g-1 after 200 cycles at 0.5 C. This study provides a new perspective for facilitating ionic conductivity and interface chemistry toward the practical feasibility of single-ion conductive polymer electrolytes.</p
