Understanding Sulfur Redox Mechanisms in Different Electrolytes for Room-Temperature Na-S Batteries

This work reports influence of two different electrolytes,carbonate ester and ether electrolytes,on the sulfur redox reactions in room-temperature Na-S batteries.Two sulfur cathodes with different S loading ratio and status are investigated.A sulfur-rich composite with most sulfur dispersed on the surface of a carbon host can realize a high loading ratio(72%S).In contrast,a confined sulfur sample can encapsulate S into the pores of the carbon host with a low loading ratio(44%S).In carbonate ester electrolyte,only the sulfur trapped in porous structures is active via‘solid-solid’behavior during cycling.The S cathode with high surface sulfur shows poor reversible capacity because of the severe side reactions between the surface polysulfides and the carbonate ester solvents.To improve the capacity of the sulfur-rich cathode,ether electrolyte with NaNO_(3) additive is explored to realize a‘solid-liquid’sulfur redox process and confine the shuttle effect of the dissolved polysulfides.As a result,the sulfur-rich cathode achieved high reversible capacity(483 mAh g^(−1)),corresponding to a specific energy of 362 Wh kg^(−1) after 200 cycles,shedding light on the use of ether electrolyte for high-loading sulfur cathode.

Revisiting the sodium-ion storage capability of hard carbon in carbonate-based electrolytes via a sodium-metal-free protocol

Common evaluation methodology of sodium(Na)-containing two-electrode or three-electrode configurations overlooks the interference from highly reactive Na metal,leading to the underestimation or inconsistent performance of low-potential hard carbon(HC)electrodes.Herein,the trap of Na metal was systematically investigated with or without applied current,uncovering its inadequacy as the reference or counter electrode in different configurations.A Na-metal-free three-electrode protocol is proposed for evaluating the actual Na^(+)-storage capability of the typical low-potential HC electrode.By avoiding Na crosstalk and precisely controlling the working electrode's potential,the actual electrochemical performance of HC in the carbonate esterbased electrolyte can be recognized with high capacity of 222 mAh g^(-1)at 2 C and 113 mAh g^(-1)at 5 C,correcting the misunderstanding of the inferior performance of HC in coin-type half cells(68%and 50%undervaluation at 2 C and 5 C,respectively).The advanced protocol is expected to reduce misunderstandings or underestimation due to evaluation methods and to guide the development of high-performance battery materials.

Synthesis of amyl ester grafted on carbon-nanopolymer composite as an inhibitor for cleaner shale drilling

Wellbore instability in oil and gas industry well drillings is a significant challenge that is linked to shale swelling when shale interacts with free water molecules in the water-based drilling fluid.Strategic design of environmentally benign,biodegradable,and effective shale hydration inhibitors is a prominent objective of contemporary exploration in well-drilling fluids as a replacement for the common KCl which is detrimental to aquatic lives.This work reports the synthesis and potential of novel green acrylic polymer-amyl ester activated carbon(-C)nanocomposite to hinder shale hydration in formations during drilling.Both less hydrophobic acrylic acid-acrylamide-activated carbon-amyl ester(AA-AAm-C-Amyl)and more hydrophobic acrylic acid-acrylamide-octadecene-activated carbon-amyl ester(AA-AAm-OD-CAmyl)composites were synthesized,characterized,and tested with standard methods as a cleaner fluid additive for shale swelling inhibition,and their results compared with that of KCl.The polymer matrixes displayed remarkable thermal stability.Results also indicate that AA-AAm-C-Amyl and AA-AAm-OD-CAmyl composites could stabilize wellbore effectively with 95.2%and 93.7%anti-swelling ratio,and shale recovery capacity of 97%and 95.2%respectively.The surface evaluation of the composite fluidtreated bentonite revealed that the mechanism of inhibition could be based on the collaborative action of nanopore plugging of carbon core and strong adsorption of the polymer component of the materials on clay surfaces via encapsulation and hydrogen bonding to form an impressive filter cake which could actively prevent water invasion into formation.Hence,AA-AAm-C-Amyl and AA-AAm-OD-C-Amyl composites could be a sustainable substitute for the conventional KCl as a shale inhibitor for welldrilling.