The development of highly active, inexpensive, and stable bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts to replace noble metal Pt and RuO
SiO is a promising alternative to Si as the anode material for lithium-ion batteries, but it still suffers from a low initial coulomb efficiency, poor electrical conductivity, unstable cycling performance, etc. Various strategies have been attempted to solve these issues but were left unsolved. In this work, we propose a simple strategy that checks all of the right boxes by presetting a lithium source electrolyte (Li2CO3) into a SiO film using the magnetron sputtering method. The preset lithium source electrolyte provides both the lithium ions and the electrolyte required for the formation of a solid electrolyte interphase and thus significantly improves the initial coulomb efficiency. The lithium source electrolyte also acts as a medium to facilitate the growth of a solid electrolyte interphase inside this composite film in addition to its surfaces. The interior interphase provides an efficient and fast pathway for lithium-ion transmission during the lithiation process and thus improves the anode conductivity and the rate performance. The interior interphase also suppresses the brittle fracture by buffering the dramatic volume change during the lithiation/delithiation process and stabilizes the cycling performance substantially. In addition, this strategy is safe, green, and of low-cost, when compared to others, and provides a feasible way to commercialize the SiO anode for lithium-ion batteries.
Thermal admittance spectroscopy is used to explain the self-healing process in the wide bandgap inorganic CsPbI 3− x Br x . It is revealed that the deep-level interstitial defects in the fresh film can be self-healed when stored in a low-humidity ambient condition.
Lithium-sulfur (Li-S) batteries have shown exceptional theoretical energy densities, making them a promising candidate for next-generation energy storage systems. However, their practical application is limited by several challenging issues, such as uncontrollable Li dendrite growth, sluggish electrochemical kinetics, and the shuttling effect of lithium polysulfides (LiPSs). To overcome these issues, we designed and synthesized hierarchical matrixes on carbon cloth (CC) by using metal-organic frameworks (MOFs). ZnO nanosheet arrays were used as anode hosts (CC-ZnO) to enable stable Li plating and stripping. The symmetric cell with CC-ZnO@Li was demonstrated to have enhanced cycling stability, with a voltage hysteresis of ∼25 mV for over 800 h at 1 mA cm-2 and 1 mAh cm-2. To address the cathode challenges, we developed a multifunctional CC-NC-Co cathode host with physical confinement, chemical anchoring, and excellent electrocatalysis. The full cells with CC-ZnO@Li anodes and CC-NC-Co@S cathodes exhibited excellent electrochemical performance, with long cycling life (0.02% and 0.03% capacity decay per cycle when cycling 900 times at 0.5 C and 600 times at 1 C, respectively) and outstanding rate performance (793 mAh g-1 at 4 C). Additionally, the pouch cell based on the flexible CC-ZnO@Li anode and CC-NC-Co@S cathode showed good stability in different bending states. Overall, our study presents an effective strategy for preparing flexible Li and S hosts with hierarchical structures derived from MOF, which can pave the way for high-performance Li-S batteries.
Porous materials such as covalent organic frameworks (COFs) are good candidates for molecular sieves due to the chemical diversity of their building blocks, which allows fine-tuning of their chemical and physical properties by design. Tailored synthesis of inherently functional building blocks can generate framework materials with chemoresponsivity, leading to controllable functionalities such as switchable sorption and separation. Herein, we demonstrate a chemoselective, salicylideneanilines-based COF (SA-COF), which undergoes solvent-triggered tautomeric switching. This is unique compared to solid-state salicylideneanilines’ counterpart, which typically requires high energy input such as photo or thermal activation to trigger the enol–keto tautomerisim and cis–trans isomerization. Accompanying the tautomerization, the ionic properties of the COF can be tuned reversibly, thus forming the basis of size-exclusion, selective ionic binding or chemoseparation in SA-COF demonstrated in this work.
Lithium-ion batteries (LIBs) are widely used as power sources for portable electronic devices. Iron oxide (mainly α-Fe2O3), as one of the most important transition metal oxide, has attracted attention due to its high theoretical capacity (1007 mAh g-1), environmental friendliness, abundance and low cost since reported as anode material for LIBs. In this thesis, an iron oxide thin film model electrode was prepared by simple thermal oxidation of pure metallic iron substrate at 300 oC in air, also used as a current collector. Electrochemical methods (CV, EIS and galvanostatic cycling) were combined with surface (XPS, ToF-SIMS) and microscopic (SEM, AFM) analytical techniques to investigate the reaction mechanisms and the surface chemistry of the iron oxide thin film at different stages of lithiation/delithiation and upon cycling.
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