Materials Today Energy最新文献

The natural abundance of sodium makes the Na-ion batteries (SIBs) attractive devices in the framework of a global economy change toward net zero CO₂ emission. SIBs naturally deliver relatively lower energy density respect to Li-ion counterparts (LiBs), however, their lower cost and fast charge/discharge-ability make them a promising competitor to LiBs to load level the intermittent power from renewable energy sources for smart grids or renewable power stations. The O3-type NaFeO₂ is a promising candidate for SIBs cathodes, even if the irreversible structural transition occurring during Na-ion extraction/insertion seriously hinders its practical application. Partial replacement of Fe by Ni significantly improves its electrochemical properties. The possible reasons of such improvement are here investigated accessing the details on the Fe and Ni local electronic and structural properties by means of x-ray absorption spectroscopy and spin-polarized DFT calculations. Different Ni concentrations and charge states have been analysed. The results support the stability of the electronic properties of Fe and Ni as a function of cycling in partially substituted system. Instead, the local structure is affected by the Fe substitution as well by the charge/discharge cycling. In particular, the decrease of Fe-O covalency and the local disorder by partial substitution Fe by Ni seems at the origin of the improved performances.

We found that the trace amount of alkylamine ligands added to perovskite solutions can act as a nucleation promoter in an anti-solvent free process. We studied the effects of adding alkylamines with different alkyl chain lengths on perovskite film formation using a 2-methoxyethanol single solvent system without adding a Lewis base solvent. Compared to a porous film prepared without additives, the film with oleylamine (OAm) containing an 18-carbon alkyl chain exhibited a smoother surface and denser interior. At optimal conditions, the perovskite solar cell with the OAm-based film exhibited an enhanced device performance of 21.01% compared to that of the pristine film (11.65%). To investigate how alkylamines support the formation of the uniform perovskite film without the assistance of a Lewis base solvent or anti-solvent process, we employed in situ grazing incidence wide-angle X-ray scattering during spin-coating. As a result, we discovered that adding OAm with longer alkyl chains leaded to more nucleation in less time promoting the formation of the dense film. Furthermore, we confirmed that the effect of OAm addition was similar in other solvent systems. Based on the results, we propose a new pathway utilizing alkylamines to control crystallization dynamics in the anti-solvent free process.

Ni-rich LiNiCoMnO₂ cathodes, which exhibit high energy densities and layered structures, have been studied For Li-ion batteries (LIBs) with high capacities and excellent stabilities. However, the high cost and price fluctuation of Co as the main element in the cathodes remain severe issue for the stable development of LIBs. Therefore, in this study, F-doped Co-free Ni-rich LiNi_xMn_1-xO₂ (0.7 ≤ x ≤ 0.9) cathodes were prepared for high-performance LIBs. With increasing Ni content, the undoped Ni-rich LiNi_xMn_1-xO₂ cathodes exhibited increased discharge capacities and decreased stabilities. In contrast, the F-doped Ni-rich LiNi_xMn_1-xO₂ cathodes delivered higher cycle retentions at 0.5 C for 100 cycles compared to the undoped cathodes. In addition, the F doping of Ni-rich LiNi_xMn_1-xO₂ cathodes can facilitate Li-ion diffusion, retaining their reversibility and high capacities at high current densities.

Li-ion-conductive sulfide electrolytes have attracted significant attention with regard to the development of superior solid-state batteries owing to their high ionic conductivity and ductile mechanical properties. Nevertheless, the relationship between the variations in Li content resulting from extraction and insertion in sulfide electrolytes and their subsequent influence on the electrochemical and mechanical properties remains unelucidated. In this study, we simulated the electrochemical operating conditions of glass sulfides through experimental and computational methods. Our investigation focused on the microscale reversibility of their electrochemical and mechanical properties. In Li-variant glass sulfides, (Li₂S)_0.75(1−x)(P₂S₅)_0.25S_0.75x, we demonstrated that 50% Li deficiency induced polymerization, resulting in a 98% decrease in Li-ion conductivity. Furthermore, we posit that changes in the mechanical properties of solid electrolytes during plastic deformation can be evaluated using Pugh’s ratio. In the case of Li deficiency, the Pugh’s ratio is reduced by 24%, and the solid electrolyte becomes extremely brittle. Interface deterioration in solid-state batteries is accelerated by the irreversible elastic hardening resulting from delithiation and polymerization of solid electrolytes during continuous electrochemical cycling. These evaluation approaches, which are based on Li-variant glass sulfides, afford guidelines for designing electrolytes suitable for cathodes.

The electron transport layer (ETL)/perovskite interfaces play a crucial role in facilitating efficient charge transfer and minimizing recombination losses, which are key factors for achieving high power conversion efficiency (PCE) in perovskite solar cells (PSCs). Herein, a novel ionic liquid (IL) called 2-bromo-1-ethylpyridinium tetrafluoroborate (BEPBF₄) is added between tin oxide (SnO₂) and perovskite layers to improve the photovoltaic performance of PSCs. The BEPBF₄ interface modification not only reduces the defect density, increases the crystallinity, and aligns the energy bands at the interface, but also shortens the lifetime of the charge carriers, resulting in improved PCE and stability. Consequently, the device modified with BEPBF₄ achieved a PCE of 20.14% and retained 94% of the initial PCE without encapsulation, in contrast to the control device (18.41%), which retained only 82% of the initial PCE after 1000 h of storage at ambient conditions. In addition, the BEPBF₄-PSCs exhibited significantly better thermal stability, retaining 64% of the initial PCE after 400 h of continuous thermal aging at 85 °C, compared to only 31% for the unencapsulated pristine device.

Oxygen vacancy (OV_ac) and interface engineering are effective tactics for regulating the electronic structure of electrocatalysts and optimizing the absorption/desorption of reactants and intermediates on the catalyst surface to enhance the oxygen evolution reaction (OER). Herein, a self-supported electrocatalyst, comprising δ-MnO₂ nanosheets grown on Co single atoms (CoSAs) anchored on N-doped carbon nanotubes (NCNTs) embedded with Co nanoparticle on a carbon cloth (CC) (δ-MnO₂/Co_NP@Co_SAs-NCNTs/CC), was fabricated. Through in-situ growth of δ-MnO₂ nanosheets on Co_NP@Co_SAs-NCNTs/CC, the number of OV_ac is increased, as proved by X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and Positron annihilation lifetime spectrometer (PALS), due to the redox between MnO₂ and Co. Experimental results and theoretical calculations confirm that the formation of OV_ac rich δ-MnO₂ nanosheets and the construction of heterogeneous interface between δ-MnO₂ and Co_SAs-NCNTs endow the electrocatalyst with good conductivity, fast charge transfer, and multiple active sites, leading to rapid OER reaction kinetics. Therefore, the δ-MnO₂/Co_NP@Co_SAs-NCNTs/CC electrocatalyst demonstrates remarkable OER performance, requiring only 165 mV overpotential to reach a current density of 10 mA cm⁻² in an alkaline solution.