Dual-Functional Organotelluride Additive for Highly Efficient Sulfur Redox Kinetics and Lithium Regulation in Lithium–Sulfur Batteries

High energy density and low cost made lithium–sulfur(Li–S)batteries appealing for the next-generation energy storage devices.However,their commercial viability is seriously challenged by serious polysulfide shuttle effect,sluggish sulfur kinetics,and uncontrollable dendritic Li growth.Herein,a dual-functional electrolyte additive,diphenyl ditelluride(DPDTe)is reported for Li–S battery.For sulfur cathodes,DPDTe works as a redox mediator to accelerate redox kinetics of sulfur,in which Te radical-mediated catalytic cycle at the solid–liquid interface contributes significantly to the whole process.For lithium anodes,DPDTe can react with lithium metal to form a smooth and stable organic–inorganic hybrid solid-electrolyte interphase(SEI),enabling homogeneous lithium deposition for suppressing dendrite growth.Consequently,the Li–S battery with DPDTe exhibits remarkable cycling stability and superb rate capability,with a high capacity up to 1227.3 mAh g^(-1)and stable cycling over 300 cycles.Moreover,a Li–S pouch cell with DPDTe is evaluated as the proof of concept.This work demonstrates that organotelluride compounds can be used as functional electrolyte additives and offers new insights and opportunities for practical Li–S batteries.

Bioorthogonal microglia-inspired mesenchymal stem cell bioengineering system creates livable niches for enhancing ischemic stroke recovery via the hormesis

Mesenchymal stem cells(MSCs)experience substantial viability issues in the stroke infarct region,limiting their therapeutic efficacy and clinical translation.High levels of deadly reactive oxygen radicals(ROS)and proinflammatory cytokines(PC)in the infarct milieu kill transplanted MSCs,whereas low levels of beneficial ROS and PC stimulate and improve engrafted MSCs’viability.Based on the intrinsic hormesis effects in cellular biology,we built a microglia-inspired MSC bioengineering system to transform detrimental high-level ROS and PC into vitality enhancers for strengthening MSC therapy.This system is achieved by bioorthogonally arming metabolic glycoengineered MSCs with microglial membrane-coated nanoparticles and an antioxidative extracellular protective layer.In this system,extracellular ROSscavenging and PC-absorbing layers effectively buffer the deleterious effects and establish a microlivable niche at the level of a single MSC for transplantation.Meanwhile,the infarct’s inanimate milieu is transformed at the tissue level into a new living niche to facilitate healing.The engineered MSCs achieved viability five times higher than natural MSCs at seven days after transplantation and exhibited a superior therapeutic effect for stroke recovery up to 28 days.This vitality-augmented system demonstrates the potential to accelerate the clinical translation of MSC treatment and boost stroke recovery.

“In-N-out” design enabling high-content triethyl phosphate-based non-flammable and high-conductivity electrolytes for lithium-ion batteries

Safety issues related to flammable electrolytes in lithium-ion batteries(LIBs) remain a major challenge for their extended applications.The use of non-flammable phosphate-based electrolytes has proved the validity in inhibiting the combustion of LIBs.However,the strong interaction between Li^(+) and phosphate leads to a dominant solid electrolyte interphase(SEI) with limited electronic shielding,resulting in the poor Li^(+) intercalation at the graphite(Gr) anode when using high-phosphate-content electrolytes.To mitigate this issue and improve Li^(+) insertion,we propose an “In-N-Out” strategy to render phosphates “noncoordinative”.By employing a combination of strongly polar solvents for a “block effect” and weakly polar solvents for a “drag effect”,we reduce the Li^(+)–phosphate interaction.As a result,phosphates remain in the electrolyte phase(“In”),minimizing their impact on the incompatibility with the Gr electrode(“Out”).We have developed a non-flammable electrolyte with high triethyl phosphate(TEP) content(>60 wt.%),demonstrating the excellent ion conductivity(5.94 mS cm^(-1) at 30 ℃) and reversible Li^(+) intercalation at a standard concentration(~1 mol L^(-1)).This approach enables the manipulation of multiple electrolyte functions and holds the promise for the development of safe electrochemical energy storage systems using non-flammable electrolytes.

A model cathode for mechanistic study of organosulfide electrochemistry in Li-organosulfide batteries

Organosulfides offer new opportunities for high performance lithium-sulfur(Li-S)batteries because of materials abundance,versatile structures and unique properties.Yet,their redox kinetics as well as cycling performance need to be further improved.Employing redox mediators is a highly effective strategy to address above challenges.However,the underlying mechanism in this chemistry is so far insufficiently explored.Here,phenyl disulfide(Ph S–SPh)and phenyl diselenide(Ph Se–Se Ph)are used as a model system for mechanistic understanding of organosulfide electrochemistry,particularly the rate acceleration.Profiling the reaction thermodynamics and charge-discharge process reveals redox of both S–S and C–S bonds,as well as that the coupling between radical exchange and electrochemical redox is the key to enhance the sulfur kinetics.This study not only establishes a basic understanding of orgaonsulfide electrochemistry in Li-S batteries,but also points out a general strategy for enhancing the kinetics of sulfur electrodes in electrochemical devices.