Operando FTIR study on water additive in lithium-sulfur batteries to mitigate shuttle effect

Additives in the electrolytes of Li-S batteries aim to increase overall capacity,improve Li ion conductivity,enhance cyclability,and mitigate the shuttle effect,which is one of the major issues of this system.Here,the use of water as an additive in the commonly used electrolyte,1.0 M LiTFSI/1.0%(w/w) LiNO_(3) and a 1:1 mixture of 1,3-dioxolane(DOL) and 1,2-dimethoxyethane(DME) was investigated.We used Co_(2)Mn_(0.5)Al_(0.5)O_(4)(CMA) as an electrocatalyst anchored on an activated carbon(AC) electrode with added sulfur via a melt-diffusion process.The structural analysis of CMA via Rietveld refinement showed interatomic spaces that can promote ionic conductivity,facilitating Li^(+) ion migration.Electrochemical tests determined 1600 ppm as the optimal water concentration,significantly reducing the shuttle effect.Post-mortem XPS analysis focused on the lithium metal anode revealed the formation of Li_(2)O layers in dry samples and LiOH in wet samples.Better capacity was observed in wet samples,which can be attributed to the superior ionic conductivity of LiOH at the electrode/electrolyte interface,surpassing that of Li_(2)O by 12 times.Finally,Operando FTIR experiments provided real-time insights into electrolyte degradation and SEI formation,elucidating the activity mechanisms of water and Li_(2)CO_(3) over the cycles.This work presents results that could aid future advancements in Li-S battery technology,offering possibilities to mitigate its challenges with inexpensive and scalable additives.

Characterization of porous cobalt hexacyanoferrate and activated carbon electrodes under dynamic polarization conditions in a sodium-ion pseudocapacitor

We report here the activated carbon and cobalt hexacyanoferrate composite,which is applied as the electrode materials in symmetric supercapacitors containing a 1.0 M Na_(2)SO_(4) aqueous electrolyte.This novel material combines high specific surface area and electrochemical stability of activated carbon with the redox properties of cobalt hexacyanoferrate,resulting in maximum specific capacitance of 329 F g^(-1) with large voltage working window of 2.0 V.Electrochemical studies indicated that cobalt hexacyanoferrate introduces important pseudocapacitive properties accounting for the overall charge-storage process,especially when I<0.5 A g^(-1).At lower gravimetric currents(e.g.,0.05 A g^(-1))and up to 1.0 V,the presence of cobalt hexacyanoferrate improves the specific energy for more than 300%.In addition,to better understanding the energy storage process we also provided a careful investigation of the electrode materials under dynamic polarization conditions using the in situ Raman spectroscopy and synchrotron light Xray diffraction techniques.Interesting complementary findings were obtained in these studies.We believe that this novel electrode material is promising for applications regarding the energy-storage process in pseudocapacitors with long lifespan properties.

Reviewing perovskite oxide sites influence on electrocatalytic reactions for high energy density devices

Batteries,fuel cells,and supercapacitors are electrochemical devices already on the market and still need a boost in kinetics to match the high energy density demand of applications.Perovskites have attracted the scientific community's attention in the last decade due to their electrocatalytic activity,chemical and structural properties,tunability,low cost,and scalability.Efforts have been made to understand the active sites and the operational mechanisms in perovskite oxides to shape them as an electrocatalyst in advanced energy devices.Understanding the role of perovskites is the key to engineering more controlled and efficient electrocatalysts via chemical synthesis,and there is still much to do.This review highlights the use of perovskites in different energy storage and conversion systems.The A,B,and A&B doping-site effects are analyzed to understand the opportunities and challenges related to this class of materials.In addition,the synthesis methods and the properties related to the doping site are described and summarized.

Synthesis and Structural Characterization of Sm-Sr Nickelates

The main purpose of this work was to obtain Sm-Sr nickelates nanoparticles with Ruddelsden-Popper type structures obtained by a simple process such as gelatin synthesis. The powders were calcinated at 900 ℃ and characterized by X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and high-resolution transmission electron microscopy techniques. The effect of chemical substitution of the Sm^3＋ by Sr^2＋ ions on the structural properties of the powders was studied. The Rietveld＇s method was successfully applied for determination of the quantitative phase analysis of the powders and revealed that the main phase of the powders for different strontium content is of Ruddelsden-Popper type structure. A symmetry change from orthorhombic to tetragonal is observed as increasing strontium.