Electrochemical interfacial catalysis in Co-based battery electrodes involving spin-polarized electron transfer

Solution-Processed MoS2-Expanded Graphite as a Fast-Charging Anode for Lithium-Ion Batteries

The widespread demand for battery-powered technologies has propelled the search for efficient and commercially viable electrode materials with fast-charging abilities. Reported herein is an MoS2-expanded graphite (EG) composite as a stable and high-rate lithium-ion battery (LIB) anode, delivering specific capacities of 796 mAh g-1 at 0.5 A g-1 and 320 mAh g-1 at 20 A g-1 over 400 cycles. Cyclability at extreme rates up to 50 A g-1 (~103 mAh g-1) illustrates its scope for fast charging applications. As a result of the processing technique, the exfoliated nanosheets have good interfacial contact which aids in charge transfer and maintaining structural integrity during continuous battery operation. Further, analytical electrochemical methods suggest a predominance of pseudocapacitive charge storage mechanism, explaining the anode performance at high rates.

Ligand engineering enhances (photo) electrocatalytic activity and stability of zeolitic imidazolate frameworks via in-situ surface reconstruction

The current limitations in utilizing metal-organic frameworks for (photo)electrochemical applications stem from their diminished electrochemical stability. In our study, we illustrate a method to bolster the activity and stability of (photo)electrocatalytically active metal-organic frameworks through ligand engineering. We synthesize four distinct mixed-ligand versions of zeolitic imidazolate framework-67, and conduct a comprehensive investigation into the structural evolution and self-reconstruction during electrocatalytic oxygen evolution reactions. In contrast to the conventional single-ligand ZIF, where the framework undergoes a complete transformation into CoOOH via a stepwise oxidation, the ligand-engineered zeolitic imidazolate frameworks manage to preserve the fundamental framework structure by in-situ forming a protective cobalt (oxy)hydroxide layer on the surface. This surface reconstruction facilitates both conductivity and catalytic activity by one order of magnitude and considerably enhances the (photo)electrochemical stability. This work highlights the vital role of ligand engineering for designing advanced and stable metal-organic frameworks for photo- and electrocatalysis.

A fast-charging/discharging and long-term stable artificial electrode enabled by space charge storage mechanism

Lithium-ion batteries with fast-charging/discharging properties are urgently needed for the mass adoption of electric vehicles. Here, we show that fast charging/discharging, long-term stable and high energy charge-storage properties can be realized in an artificial electrode made from a mixed electronic/ionic conductor material (Fe/LixM, where M = O, F, S, N) enabled by a space charge principle. Particularly, the Fe/Li2O electrode is able to be charged/discharged to 126 mAh g-1 in 6 s at a high current density of up to 50 A g-1, and it also shows stable cycling performance for 30,000 cycles at a current density of 10 A g-1, with a mass-loading of ~2.5 mg cm-2 of the electrode materials. This study demonstrates the critical role of the space charge storage mechanism in advancing electrochemical energy storage and provides an unconventional perspective for designing high-performance anode materials for lithium-ion batteries.

Rose-like NiCo2O4 with Atomic-Scale Controllable Oxygen Vacancies for Modulating Sulfur Redox Kinetics in Lithium-Sulfur Batteries

The long-term stability of Li-S batteries is significantly compromised by the shuttle effect and insulating nature of active substance S, constraining their commercialization. Developing efficient catalysts to mitigate the shuttle effect of lithium polysulfides (LiPSs) is still a challenge. Herein, we designed and synthesized a rose-like cobalt-nickel bimetallic oxide catalyst NiCo2O4-OV enriched with oxygen vacancies (OV) and verified the controllable synthesis of different contents of OV. Introducing the OV proved to be an efficient approach for controlling the electronic structure of the electrocatalyst and managing the absorption/desorption processes on the reactant surface, thereby addressing the challenges posed by the LiPS shuttle effect and sluggish transformation kinetics in Li-S batteries. In addition, we investigated the effect of OV in NiCo2O4 on the adsorption capacity of LiPSs using adsorption experiments and density functional theory (DFT) simulations. With the increase in the level of OV, the binding energy between the two is enhanced, and the adsorption effect is more obvious. NiCo2O4-OV contributes to the decomposition of Li2S and diffusion of Li+ in Li-S batteries, which promotes the kinetic process of the batteries.

Real-time tracking of electron transfer at catalytically active interfaces in lithium-ion batteries

Transition metals and related compounds are known to exhibit high catalytic activities in various electrochemical reactions thanks to their intriguing electronic structures. What is lesser known is their unique role in storing and transferring electrons in battery electrodes which undergo additional solid-state conversion reactions and exhibit substantially large extra capacities. Here, a full dynamic picture depicting the generation and evolution of electrochemical interfaces in the presence of metallic nanoparticles is revealed in a model CoCO3/Li battery via an in situ magnetometry technique. Beyond the conventional reduction to a Li2CO3/Co mixture under battery operation, further decomposition of Li2CO3 is realized by releasing interfacially stored electrons from its adjacent Co nanoparticles, whose subtle variation in the electronic structure during this charge transfer process has been monitored in real time. The findings in this work may not only inspire future development of advanced electrode materials for next-generation energy storage devices but also open up opportunities in achieving in situ monitoring of important electrocatalytic processes in many energy conversion and storage systems.