ABSTRACT
Lithium-oxygen batteries possess an extremely high theoretical energy density, rendering them a prime candidate for next-generation secondary batteries. However, they still face multiple problems such as huge charge polarization and poor cycle life, which lay a significant gap between laboratory research and commercial applications. In this work, we adapt 15-crown-5 ether (C15) as solvent to regulate the generation of discharge products in lithium-oxygen batteries. The coronal structure endows C15 with strong affinity to Li+, firmly stabilizes the intermediate LiO2 and discharge product Li2O2. Thus, the crystalline Li2O2 is amorphized into easily decomposable amorphous products. The lithium-oxygen batteries assembled with 0.5 M C15 electrolyte show an increased discharge capacity from 4.0 mAh cm-2 to 5.7 mAh cm-2 and a low charge overpotential of 0.88 V during the whole lifespan at 0.05 mA cm-2. The batteries with 1 M C15 electrolyte can cycle stably for 140 cycles. Furthermore, the amorphous characteristic of Li2O2 product is preserved when matched with redox mediators such as LiI, with the charge polarization further decreasing to 0.74 V over a cycle life of 190 cycles. This provides new possibilities for electrolyte design to promote Li2O2 amorphization and reduce charge overpotential in lithium-oxygen batteries.
ABSTRACT
Application of silicon-based anodes is significantly challenged by low initial Coulombic efficiency (ICE) and poor cyclability. Traditional pre-lithiation reagents often pose safety concerns due to their unstable chemical nature. Achieving a balance between water-stability and high ICE in prelithiated silicon is a critical issue. Here, we present a lithium-enriched silicon/graphite material with an ultra-high ICE of ≥110 % through a high-stable lithium pre-storage methodology. Lithium pre-storage prepared a nano-drilled graphite material with surficial lithium functional groups, which can form chemical bonds with adjacent silicon during high-temperature sintering. This results in an unexpected O-Li-Si interaction, leading to in situ pre-lithiation of silicon nanoparticles and providing high stability in air and water. Additionally, the lithium-enriched silicon/graphite materials impart a combination of high ICE, high specific capacity (620â mAh g-1), and long cycling stability (>400 cycles). This study opens up a promising avenue for highly air- and water-stable silicon anode prelithiation methods.
ABSTRACT
The energy efficiency of metal-air batteries and water-splitting techniques is severely constrained by multiple electronic transfers in the heterogenous oxygen evolution reaction (OER), and the high overpotential induced by the sluggish kinetics has become an uppermost scientific challenge. Numerous attempts are devoted to enabling high activity, selectivity, and stability via tailoring the surface physicochemical properties of nanocatalysts. Lattice-strain engineering as a cutting-edge method for tuning the electronic and geometric configuration of metal sites plays a pivotal role in regulating the interaction of catalytic surfaces with adsorbate molecules. By defining the d-band center as a descriptor of the structure-activity relationship, the individual contribution of strain effects within state-of-the-art electrocatalysts can be systematically elucidated in the OER optimization mechanism. In this review, the fundamentals of the OER and the advancements of strain-catalysts are showcased and the innovative trigger strategies are enumerated, with particular emphasis on the feedback mechanism between the precise regulation of lattice-strain and optimal activity. Subsequently, the modulation of electrocatalysts with various attributes is categorized and the impediments encountered in the practicalization of strained effect are discussed, ending with an outlook on future research directions for this burgeoning field.
