Cunman Zhang

Operating proton-exchange membrane fuel cells (PEMFCs) under near-boiling-point conditions is considered promising for heavy-duty applications; however, elevated temperatures and insufficient hydration can intensify mass transport limitations in the catalyst layer (CL). Although regulating the side-chain structure of PFSA ionomers is an effective strategy to improve high-temperature performance, the relationship between ionomer architecture, CL microstructure, and transport behavior remains insufficiently understood. Herein, a systematic comparison between a long-side-chain (LSC) ionomer (Nafion-117) and a short-side-chain (SSC) ionomer (D79) was conducted using single-cell measurements at 75 and 105 °C, with polarization tests performed at 40% and 80% RH and cyclic voltammetry (CV) measurements conducted at 100% RH. The effects of ionomer structures on catalyst ink dispersion, CL morphology, pore characteristics, and electrochemical transport behavior were investigated. The results demonstrate that D79 exhibits superior performance under near-boiling-point conditions, accompanied by higher Pt utilization and lower ohmic and concentration losses, particularly at high current densities and low humidity. D79 also forms a more open and heterogeneous pore structure, which is consistent with its more favorable high-current-density transport behavior. Polarization loss decomposition further indicates that the performance advantage of D79 is mainly associated with reduced ohmic and concentration polarization losses under near-boiling-point and low-humidity conditions. These findings clarify the influence of PFSA side-chain structure on CL microstructure and electrochemical transport behavior and provide experimental insights for the design of PFSA ionomers for near-boiling-point PEMFC operation.

Gel polymer electrolytes (GPEs) rich in ether oxygen side chains have attracted particular interests in high‑energy‑density lithium metal batteries (LMBs). However, the strong coordination between their polymer framework and lithium ions (Li ⁺ ) leads to a high desolvation energy barrier at low temperatures. Herein, by comparing the side‑chain electronic effects, this work constructs an ether‐oxygen‐based gel polymer electrolyte (E‐GPE) with electron‐donating ether oxygen side chains and a fluorinated GPE (F‐GPE) with electron‐withdrawing trifluoromethyl side chains, with N,N‐dimethyl trifluoroacetamide (FDMA) as a low‐temperature additive. Density functional theory (DFT) calculations reveal that the electron‐donating side chains in E‐GPE enhance the binding energy between the polymer framework and Li ⁺ , thereby impeding Li ⁺ desolvation. Conversely, the electron‐withdrawing side chains in F‐GPE weaken the binding energy between the polymer framework and Li ⁺ , lowering the Li ⁺ desolvation barrier and inducing the formation of LiF‐rich interphase. Consequently, Li/F‐GPE/Li cells stably cycle for over 1000 h at −20°C, and Li/F‐GPE/LiCoO ₂ coin cells retain 88.7% of their original capacity after 400 cycles at −20°C. Furthermore, pouch cells steadily power a light‐emitting diode (LED) after shear damage, demonstrating potential safety. This work provides a new design paradigm for developing GPEs for high‐energy‐density LMBs in extreme environments.

High-temperature (>100 °C) operation of proton exchange membrane fuel cells simplifies water and thermal management, accelerates electrode kinetics, and improves impurity tolerance. However, the degradation mechanism of the membrane electrode assembly (MEA) under such conditions remains unclear. Here, a high-temperature-resistant MEA based on a phosphoric–sulfonic acid copolymer membrane is investigated through an accelerated stress test at 105 °C for 50 h. The initiation and propagation of crack networks within the cathode catalyst layer are identified as a critical bottleneck in performance degradation. Mass transport loss is the most pronounced degradation mode. This loss arises from crack formation, ionomer degradation, and carbon corrosion. The MEA exhibits a voltage decay of 35.23% at 2 A cm–2 and an electrochemical surface area loss of 62.9%. Chemically, cracks initiate from the transformation of disordered carbon into ordered carbon in the carbon support (ID/IG decreasing from 1.1268 to 0.4735) and the detachment of sulfonic acid side chains from the ionomer (I1060/I1210 decreasing from 0.483 to 0.133). Physically, Ostwald ripening of platinum particles (mean size increasing from 3.48 to 4.29 nm) and stress concentration induced by temperature and humidity cycling drive crack growth. Finite-element simulations using a cohesive zone model reveal that cracks propagate steadily along the ionomer/catalyst interface─the path of least energy dissipation. This study establishes a direct link from microstructural evolution to macroscopic performance degradation. Crack network formation is highlighted as a key bottleneck. These findings provide guidance for material design and lifetime prediction of high-temperature-resistant MEAs.

A Y-MoO _3−x shell layer is constructed on the surface of Ni ₄ Mo alloy. The Y–O–Mo bond energy inhibits the dissolution of Mo species. Meanwhile, the oxygen vacancies can act as Lewis acid sites, accelerating the rate of water molecule dissociation.

Anode‐free sodium metal batteries (AFSMBs) forgo the excess metallic sodium anode, thus offering a compelling route to simultaneously enhance energy density and simplify manufacturing. However, their practical deployment is fundamentally limited by the irreversible depletion of active sodium, a consequence of inherently unstable interfacial chemistry and the stringent constraint of finite sodium inventory. In this review, we introduce theoretical reversibility as a unifying criterion to categorize the dominant sodium loss pathways. By integrating thermodynamic principles with kinetic analysis, we systematically deconvolute the intricate mechanisms of capacity degradation by tracking the migration and deposition behavior of Na ⁺ ions. Furthermore, we present a comprehensive taxonomy of state‐of‐the‐art strategies for mitigating capacity fade, which are anchored in the dual pillars of uniform Na nucleation/growth and regulated solid electrolyte interphase (SEI) formation/evolution. Special emphasis is placed on stacking stress, a critical yet underappreciated factor that dictates the morphological evolution of sodium deposits. Finally, we delineate the current fundamental bottlenecks and outline promising avenues for future research to accelerate the development of high‐performance AFSMBs.

Battery thermal management under ultra-high-power pulse loads is constrained by a fundamental conflict between electrochemical fidelity and system-level design feasibility. Real racing loads contain sharp current peaks, high-frequency fluctuations, regenerative events, and long-duration dynamic sequences, which amplify transient heat generation and make direct high-fidelity electrochemical-thermal simulation impractical for accumulator-level cooling design. To address this issue, this study develops an efficient multiscale framework that converts real pulse-load data into spatially resolved thermal loading and heat-source-guided cooling design. A pseudo-two-dimensional (P2D) electrochemical-thermal model was established to resolve pouch-cell heat generation, while a physics-consistent load reconstruction strategy was introduced to suppress numerical stiffness without discarding the dominant pulse morphology or Ohmic heat-generation scale. The reconstructed load limited the current-squared energy deviation to 2.56% and reduced the P2D solving time from approximately 8 h to 46 s. The calibrated pouch-cell response was then transferred to module and accumulator scales through normalized heat-source mapping, avoiding the need to solve the full electrochemical model for every cell. Module-level analysis showed that passive cooling and natural convection were insufficient under the selected endurance condition, and that an effective convective heat-transfer coefficient above approximately 30 W m−2 K−1 was required to keep the battery temperature below the conservative 323 K design threshold. The corrected heat-source distribution was further converted into a target airflow field, enabling surrogate-assisted cooling-channel screening followed by full computational fluid dynamics (CFD) verification. The selected design achieved an estimated average convective heat-transfer coefficient of approximately 37 W m−2 K−1 in the heat-generating cell regions. Real-vehicle track tests further showed that the battery temperature remained below the prescribed limit and that the measured temperature-rise trend was consistent with the predicted trend. This work provides a computationally efficient route from real pulse-load data to verified accumulator-level battery thermal management design under ultra-high-power pulse loads.

Anion exchange membrane water electrolysis (AEMWE) holds promise as a low‐cost, efficient hydrogen production method, but its internal polarization mechanisms remain poorly resolved. A precisely controlled single‐cell experimental platform is developed to completely decouple ionic transfer, charge transfer, and mass transfer processes under realistic operating conditions. Distribution of relaxation times (DRT) analysis assigns each resolved spectral peak to specific polarization processes, and the assignments are validated through carefully designed variations in membrane thickness, electrocatalysts, temperature, and flow rate. Based on these results, a frequency‐mechanism map is constructed and applied to quantify impedance evolution across a wide range of current densities. The shifting contributions of dominant polarization processes are clearly revealed, and a robust, experimentally supported framework for interpreting impedance spectra in AEM systems is established. This work provides a mechanism‐specific diagnostic reference and guidance for future optimization and control strategies in AEM electrolyzers.

The combination of lithium metal anodes and high-load Li-rich Mn-based cathodes (LMLO, Li_1.2Mn_0.54Co_0.13Ni_0.13O₂) empowers lithium metal batteries (LMBs) to reach energy densities above 500 W h kg^-1. However, sluggish kinetics, continuous interfacial reactions, and serious safety concerns impede their practical application. Herein, a flame-retardant carbonate-based electrolyte containing hexafluorocyclotriphosphazene (HFPN), lithium difluoro(oxalato) borate (LiDFOB), and 1-butyl-2,3-dimethylimidazolium nitrate (BDIN) coadditives has been designed to enable 528 W h kg^-1 LMBs with enhanced safety performance by synchronously regulating the formation of kinetically enhanced cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI). Specifically, flame-retardant HFPN facilitates the formation of a stable CEI enriched with P-, F-, and N-containing inorganic species, thereby improving the thermal stability and Li⁺ transport kinetics. LiDFOB participates in forming a fast Li⁺ conducting SEI on the lithium metal anode, while the interaction between BDIN and FEC promotes the decomposition of FEC to induce an F-containing organic matter SEI, which achieves a Coulombic efficiency exceeding 95.9% in the Li||Cu cell. As a result, an LMLO||Li full cell with 6.4 mA h cm^-2 delivers a capacity of 272 mA h g^-1 and 94.7% retention after 50 cycles. This strategy for the interphase regulation and safety enhancement by synergistic additives can practically be extended to other high-energy lithium-ion batteries.

Sacrificial sodium-rich salts pre-sodiation is a safe and promising approach to supplement sodium-ion batteries with additional capacity for energy density enhancement. However, high-cost from additional solvent and low-utilization-ratio caused by loose electrical contact limit its practical application in slurry-coated electrodes. Herein, we demonstrate a dry-processing method to enable complete sodium oxalate decomposition and solvent-free production of thick electrodes. Distinct to particle aggregation in slurry-coated electrodes, a homogenous mixture of Na₂C₂O₄ and conductive agents is generated and wraps Na₃V₂(PO₄)₃ particles after high-speed shear-mixing and hot-calendaring of dry-processing method, constructing intimate and durable electronic pathways, thus realizing theoretical decomposition capacity of Na₂C₂O₄ in thick electrodes (54 mg cm^-2). This strategy increases the lifespan by 200 cycles and energy density by 82.5% for all-dry-processing sodium-ion batteries with areal capacity of 5.4 mAh cm^-2, which highlights the vital role of exploiting mechanical and thermal effects of dry-processing method in sustainable fabrication of high-energy sodium-ion batteries.