In situ characterizations of advanced electrode materials for sodium-ion batteries toward high electrochemical performances

Energy storage is an ever-growing global concern due to increased energy needs and resource exhaustion.Sodium-ion batteries(SIBs)have called increasing attention and achieved substantial progress in recent years owing to the abundance and even distribution of Na resources in the crust,and the predicted low cost of the technique.Nevertheless,SIBs still face challenges like lower energy density and inferior cycling stability compared to mature lithium-ion batteries(LIBs).Enhancing the electrochemical performance of SIBs requires an in-deep and comprehensive understanding of the improvement strategies and the underlying reaction mechanism elucidated by in situ techniques.In this review,commonly applied in situ techniques,for instance,transmission electron microscopy(TEM),Raman spectroscopy,X-ray diffraction(XRD),and X-ray absorption near-edge structure(XANES),and their applications on the representative cathode and anode materials with selected samples are summarized.We discuss the merits and demerits of each type of material,strategies to enhance their electrochemical performance,and the applications of in situ characterizations of them during the de/sodiation process to reveal the underlying reaction mechanism for performance improvement.We aim to elucidate the composition/structure-per formance relationship to provide guidelines for rational design and preparation of electrode materials toward high electrochemical performance.

In situ tracking of the lithiation and sodiation process of disodium terephthalate as anodes for rechargeable batteries by Raman spectroscopy

Organic compounds represent an appealing group of electrode materials for rechargeable batteries due to their merits of biomass,sustainability,environmental friendliness,and processability.Disodium terephthalate(Na_(2)C_(8)H_(4)O_(4),Na_(2)TP),an organic salt with a theoretical capacity of 255 mAh·g^(-1),is electroactive towards both lithium and sodium.However,its electrochemical energy storage(EES)process has not been directly observed via in situ characterization techniques and the underlying mechanisms are still under debate.Herein,in situ Raman spectroscopy was employed to track the de/lithiation and de/sodiation processes of Na2TP.The appearance and then disappearance of the–COOLi Raman band at 1625 cm^(-1) during the de/lithiation,and the increase and then decrease of the–COONa Raman band at 1615 cm^(-1) during the de/sodiation processes of Na2TP elucidate the one-step with the 2Li+or 2Na+transfer mechanism.We also found that the inferior cycling stability of Na2TP as an anode for sodium-ion batteries(SIBs)than lithium-ion batteries(LIBs)could be due to the larger ion radium of Na+than Li+,which results in larger steric resistance and polarization during EES.The Na2TP,therefore,shows greater changes in spectra during de/sodiation than de/lithiation.We expect that our findings could provide a reference for the rational design of organic compounds for EES.

In situ Raman,FTIR,and XRD spectroscopic studies in fuel cells and rechargeable batteries

As state-of-the-art electrochemical energy conversion and storage(EECS)techniques,fuel cells and rechargeable batteries have achieved great success in the past decades.However,modern societies’ever-growing demand in energy calls for EECS devices with high efficiency and enhanced performance,which mainly rely on the rational design of catalysts,electrode materials,and electrode/electrolyte interfaces in EESC,based on in-deep and comprehensive mechanistic understanding of the relevant electrochemical redox reactions.Such an understanding can be realized by monitoring the dynamic redox reaction processes under realistic operation conditions using in situ techniques,such as in situ Raman,Fourier transform infrared(FTIR),and X-ray diffraction(XRD)spectroscopy.These techniques can provide characteristic spectroscopic information of molecules and/or crystals,which are sensitive to structure/phase changes resulted from different electrochemical working conditions,hence allowing for intermediates identification and mechanisms understanding.This review described and summarized recent progress in the in situ studies of fuel cells and rechargeable batteries via Raman,FTIR,and XRD spectroscopy.The applications of these in situ techniques on typical electrocatalytic electrooxidation reaction and oxygen reduction reaction(ORR)in fuel cells,on representative high capacity and/or resource abundance cathodes and anodes,and on the solid electrolyte interface(SEI)in rechargeable batteries are discussed.We discuss how these techniques promote the development of novel EECS systems and highlight their critical importance in future EECS research.

Surface-Enhanced Raman Spectroscopy:Principles,Methods,and Applications in Energy Systems

Surface-enhanced Raman spectroscopy(SERS)has advanced significantly since its inception.Numerous experimental and theoretical efforts have been made to understand the SERS effect and demonstrate its potential.Due to its extremely high sensitivity and selectivity and ability to provide molecular fingerprint information,SERS has a wide range of applications in surface and interfacial chemistry,energy,materials,biomedicine,environmental analysis,etc.This review aims to provide readers with an understanding of the principles,methodologies,and applications of SERS.We briefly introduce the fundamental theory of the SERS enhancement mechanism and summarize the details of the preparation of SERS-active substrates.Recent applications of SERS in energy systems are then highlighted,including probing surface reactions and interfacial charge transfer of batteries and electrocatalysts.Finally,the challenges and prospects of SERS research are discussed.

Plasmonic photocatalysis:Mechanism,applications and perspectives

The process of photocatalysis,regarded as a promising approach for tackling the energy crisis and environmental pollution issues,is crucial for turning solar light into chemical resources.However,the solar-chemical conversion efficiency of typical semiconductor catalysts is still too low,so it is vital to figure out how to boost photocatalytic performance of semiconductors.Under visible light illumination,the local surface plasmon resonance(LSPR)induced by coinage metal would enhance the local electric field and improve photocatalytic performance of semiconductors,especially in the visible range.Therefore,its attachment to semiconductors has been regarded as an efficient strategy to improve photocatalytic performance.This paper reviews the latest research progress of plasmonic photocatalysis from theory to application.Starting from the excitation and relaxation of plasmons,four main mechanisms of plasmon-enhanced semiconductor photocatalysis are introduced,including enhanced light absorption and scattering,local electromagnetic field enhancement,improved hot carriers(HCs)injection and enhanced thermal effect.Secondly,the current mainstream plasmonic photocatalysts,such as monometallic,bimetallic and non-noble metal-based plasmonic catalysts,are reviewed.Finally,the applications of plasmonic photocatalysts in H_(2) production,CO_(2) reduction,and antibacterial are further summarized.