ACS Applied Energy Materials最新文献

Aqueous zinc-ion batteries (AZIBs) are promising energy storage systems due to their intrinsic safety, high volumetric energy density, low reduction potential, and the abundance of zinc. However, challenges such as dendrite formation and parasitic side reactions hinder their large-scale commercialization. In this study, we synthesized a polydiacetone acrylamide @ acrylamide (PAD) coating in situ on zinc foil to solve these problems. The coating inhibits side reactions by preventing water from contacting the zinc surface. The functional groups on the coating facilitate uniform deposition of Zn between the coating and the zinc foil, which is beneficial to improve battery life. PAD has “water respiration”, which can effectively reduce the mechanical performance degradation caused by polymer coating swelling. As a result, the symmetric cell demonstrated a remarkable cycling stability of 1200 h at 10 mA cm^–2 and 10 mAh cm^–2. The asymmetric cell achieved over 600 cycles (∼1.7 months) with an average Coulombic efficiency of 99.5% at 1 mA cm^–2 and 1 mAh cm^–2. Furthermore, the full cell exhibited 5600 cycles with 93.4% capacity retention at 5 A g^–1 and 8 mg cm^–2 mass loading. This work provides a simple and effective strategy: in situ “water respiration” coating significantly improves the cycling performance of zinc-ion batteries and demonstrates an improved idea for aqueous zinc storage devices.

Self-supported electrodes are increasingly being used in anion exchange membrane electrolyzers. However, a clear understanding of the effects of substrate chemistry and structure is lacking. NiMoO₄ nanorods were hydrothermally grown from sodium molybdate and ammonium heptamolybdate precursors onto a series of porous electrode supports, including Ni foams and felts, and sintered metal-fiber-derived porous transport layers made of Ni, stainless steel, and Hastelloy-X. The Mo precursor primarily influenced the growth mechanism, while substrate architecture controlled morphology and anchoring behavior. When implemented as cathodes in an anion exchange membrane water electrolyzer, the electrodes exhibited substrate-dependent activation behavior at the beginning of life, which was linked to the spatial accessibility of the nanorods. However, their electrochemical performance converged during steady-state operation after more than 70 h, regardless of precursor or substrate. These results establish a mechanistic basis connecting precursor chemistry, substrate selection, and structural development, enabling rational integration of NiMo₄-based self-supported electrodes into fully PGM-free alkaline electrolyzer platforms.

Covalent organic frameworks (COFs) are attractive photocatalyst platforms because their electronic structures can be chemically tailored, yet overall water splitting requires the simultaneous optimization of framework stability, interfacial charge separation, carrier utilization, and surface redox thermodynamics. Here, we use transition-metal coordination as a chemical design handle to investigate COF/HfX₂ (X = S, Se) heterostructures as candidates for a proposed direct Z-scheme configuration from TpMA-COF monolayers. Screening of a series of coordinated TpMA-COFs shows that Ti- and Zr-coordinated frameworks provide the most suitable building blocks, as they preserve the COF backbone, remain nonmagnetic, and exhibit narrowed band gaps with band-edge positions more favorable for hydrogen evolution than those of pristine TpMA-COF. When coupled with HfX₂, these coordinated COFs form energetically favorable interfaces with pronounced charge redistribution, work-function-driven built-in electric fields, and complementary redox functions. State-resolved nonadiabatic molecular dynamics further differentiate the relative tendencies of selected electron-transfer, hole-transfer, and interband-recombination pathways among the four heterostructures, providing comparative insight into possible carrier-loss processes that may limit the proposed direct Z-scheme operation. Gibbs free-energy analysis indicates that the photocatalytic feasibility of the selected heterostructures is strongly pH dependent, with sulfide-based systems favored under acidic conditions and selenide-based systems becoming more viable in alkaline media. These results identify transition-metal coordination as a chemically useful strategy for linking frontier-state regulation, interfacial field formation, carrier-loss assessment, and pH-dependent reaction feasibility in COF-based heterostructure photocatalysts.

Carbon-based HTL-free CsPbI_2.75Br_0.25 all-inorganic perovskite solar cells face challenges from interfacial defects and suboptimal energy-level alignment. In this work, tetramethylammonium acetate (TMMAc) is employed for the first time as a multifunctional surface modifier to concurrently address these issues. TMMAc features a unique zwitterionic structure that enables synergistic passivation: its acetate anion (CH₃COO^–) acts as a strong Lewis base, exhibiting strong interaction with uncoordinated Pb²⁺ ions, thereby effectively passivating lead-related defects. Meanwhile, its tetramethylammonium cation ((CH₃)₄N⁺) passivates halogen vacancies. Moreover, the intrinsic strong polarity of TMMAc and the formed oriented dipole layer at the interface modulate the surface work function, inducing a favorable gradient energy-level alignment between the perovskite and the carbon electrode, which significantly reduces the hole extraction barrier. As a result, the TMMAc-modified device achieves a PCE of 17.93% and an open–circuit voltage of 1.19 V, along with markedly improved operational stability.

The rapid growth of flexible and wearable electronics has created an increasing demand for lithium-ion batteries that can maintain high electrochemical performance while withstanding repeated mechanical deformation. In this research, we investigate the incorporation of single-walled carbon nanotubes (SWCNTs) as a conductive carbon dopant together with a polymer binder (VT475) in LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) cathodes. SWCNTs play a dual role in cathode performance. Mechanically, their one-dimensional nanostructure mitigates particle pulverization and improves tolerance to mechanical deformation (e.g., bending), which is essential for flexible and wearable applications. Electrochemically, SWCNTs form a percolated conductive network within the cathode, significantly improving electronic conductivity and facilitating efficient electron transport. This synergistic effect enhances capacity retention and cycling stability, even at high C-rates (132 mAh/g@5C). Pouch cells incorporating the SWCNT-doped cathodes were extensively characterized using galvanostatic testing at various C-rates, long-term cycling (1000 cycles), electrochemical impedance spectroscopy, and adhesion testing (ASTM D3359), among other methods. Relative to reference electrodes, the SWCNT-doped cathodes demonstrate synergistic improvement in electrochemical and mechanical performance. Based on the experimental results, a physics-informed semiempirical formulation model is developed to describe how the binder content influences the electrochemical and mechanical performance of the cathodes. The model supports slurry formulation selection by mapping the trade-off between rate capability, cycling stability, and adhesion according to application requirements.

A systematic comparative study of Ti₃C₂T_x, Nb₂CT_x, Nb₄C₃T_x, and V₄C₃T_x MXenes synthesized via a fluoride–salt (HCl + LiF) etching route is presented to elucidate the influence of MXene phase and stoichiometry on their electrochemical behavior in sulfuric acid. Structural and surface characterizations confirmed the successful exfoliation of the MXenes, revealing distinct morphologies and varying degrees of functionalization. The operating potential window was rigorously determined by combining cyclic voltammetry, galvanostatic charge–discharge, chronoamperometry, and electrochemical impedance spectroscopy. Ti₃C₂T_x exhibited enhanced cathodic stability (−0.5 V vs Ag/AgCl), whereas Nb- and V-based phases showed slightly narrower negative limits (∼−0.4 V vs Ag/AgCl). In addition, M₄C₃ structures demonstrated improved anodic tolerance. At 0.5 A g⁻¹, specific capacitances of 225.3, 140.1, 190.6, and 131.5 F g⁻¹ were obtained for Ti₃C₂T_x, Nb₂CT_x, Nb₄C₃T_x, and V₄C₃T_x, respectively. Dunn’s analysis revealed predominantly capacitive charge storage at 10 mV s⁻¹ (94−85%), with diffusion contributions becoming more significant at low scan rates, particularly for the M₄C₃ phases. Therefore, the results demonstrate that MXene electrochemical performance is strongly influenced by structural stoichiometry, while also reflecting the coupled effects of surface chemistry, morphology, and interlayer structure, which collectively modulate stability limits and charge-storage kinetics in sulfuric acid.

Microencapsulated phase change materials for battery thermal regulation require efficient heat transport during normal operation and thermal resistance during thermal runaway propagation. MXene modified inorganic phase change microcapsules (IPCM/MXene) were prepared by inverse emulsion interfacial sol−gel encapsulation using disodium hydrogen phosphate dodecahydrate as the core and SiO₂ as the shell. Ti₃C₂T_x MXene bridged adjacent microcapsules, increasing thermal conductivity by 70.5% while retaining 93.7% of the melting enthalpy of unmodified IPCM. Under high temperature condition, thermal conductivity decreased by 54.6% following MXene oxidation and inorganic residue formation. In 18650 cell tests, IPCM/MXene reduced the peak temperature from 44.7 to 33.7 °C at 3C discharge and maintained stable cooling during repeated cycling. During thermal runaway propagation, the triggering of thermal runaway was delayed by 1899–1970 s, while the interval between the second and third cells increased from 122 to 193 s. These results establish a nonflammable microcapsule design for battery thermal management and safety protection.

Hard carbon represents a highly promising option for anodes in sodium-ion batteries, yet its application is constrained by insufficient plateau capacity, unsatisfactory initial Coulombic efficiency, and the still-debated sodium storage mechanism. This paper details the pioneering use of biphenyl phenolic novolac resin as a precursor for hard carbon anodes. The hard carbon derived from pyrolysis undergoes systematic structural changes, including reduced defect and oxygen contents, decreased specific surface area, enhanced local ordering, tuned interlayer spacing, and enlarged nanopore size, by controlling the pyrolysis temperature. These structural changes collectively promote both the plateau capacity and the overall reversible capacity. The optimized sample pyrolyzed at 1600 °C delivers a high reversible capacity of 387.7 mAh g^–1 at 20 mA g^–1, together with an initial Coulombic efficiency of 84.6%, and maintains 76% capacity retention after 2000 cycles at 500 mA g^–1. Combining electrochemical kinetics analysis with in situ Raman spectroscopy, we identify an adsorption-intercalation-filling sodium storage mechanism, in which Na⁺ adsorption on surface defects contributes mainly to the sloping capacity, whereas Na⁺ intercalation into turbostratic carbon layers and subsequent filling of nanopores dominate the low-voltage plateau capacity. In addition to presenting a resin precursor for high-performance hard carbon anodes, this work provides mechanistic insights into the regulation of microstructure for plateau-dominated sodium storage.

Sodium-ion batteries (SIBs) have emerged as promising alternatives for large-scale energy storage owing to the abundance and low cost of sodium. However, layered oxide cathodes suffer from severe surface degradation and irreversible phase transitions during high-voltage cycling, limiting their electrochemical performance. Here, we report an ultrathin sodium-ion conductive nanolayer composed of a Na–Ni–Fe–Mn–Ti–O multicomponent oxide with a cubic NaTiO₂-type framework (NTO), formed on NaNi_1/3Fe_1/3Mn_1/3O₂ (NFM) via atomic layer deposition followed by thermal annealing. The conformal NTO layer (∼2–3 nm) preserves the bulk crystal structure and particle morphology. As a result, the NTO-coated NFM exhibits significantly improved electrochemical performance, delivering approximately fivefold higher capacity retention after 400 cycles at 0.2 C and sixfold higher discharge capacity at 1 C compared to pristine NFM. Structural and interfacial analyses reveal that the NTO layer suppresses surface degradation and inhibits the formation of a cation-disordered rock-salt phase. In situ X-ray diffraction further shows that the NTO layer induces a more solid-solution-like phase transition, enabling reversible structural evolution. This behavior is attributed to the Na concentration gradient between the surface layer and bulk, which enhances Na⁺ transport and alleviates structural strain. These results demonstrate that constructing an ultrathin Na-ion conductive interfacial layer is an effective strategy to improve the structural stability and electrochemical performance of layered oxide cathodes.

Although vanadium redox flow batteries (VRFBs) hold significant promise for large-scale, long-duration energy storage, their practical deployment at elevated temperatures is severely hindered by the poor thermal stability of the positive electrolyte. In this work, a Na₃PO₄/CTAB composite additive was introduced into vanadium electrolytes to enhance high-temperature stability. Compared with single-additive systems, the composite additive exhibited a distinct synergistic effect by suppressing precipitation of the positive electrolyte while maintaining or improving interfacial redox kinetics. As a result, the precipitation rate of vanadium at 50 °C decreased by 11.67% relative to that of the pristine electrolyte. At 55 °C and a current density of 80 mA cm^–2, the cell containing the composite additive delivered an energy efficiency of 85.72% after 60 cycles, and its discharge capacity reached 876.73 mAh, significantly higher than that of the cell with the pristine electrolyte (497.70 mAh). Mechanistic analyses indicate that phosphate enhances bulk electrolyte stability, whereas CTAB mitigates the interfacial aggregation and deposition of vanadium species. These findings demonstrate that the rational design of composite additives offers an effective and practical strategy for broadening the operating temperature window of VRFB electrolytes.