Li-O_(2) batteries provide an attractive and potential strategy for energy conversion and storage with high specific energy densities.However,large over-potential in oxygen evolution reactions (OER) caused by the deco...Li-O_(2) batteries provide an attractive and potential strategy for energy conversion and storage with high specific energy densities.However,large over-potential in oxygen evolution reactions (OER) caused by the decomposition obstacles of Li_(2)O_(2) seriously impedes its electrochemical performances.Herein,a novel N,O,S and F co-doping vesicular carbon was prepared by self-template pyrolysis method and used in LiO_(2) battery to tune the nucleation and decomposition of Li_(2)O_(2).The introduction of F in the carbon matrix with suitable content can regulate the adsorption of intermediates,through which the morphology of Li_(2)O_(2) can be controlled to film,favorable to its decomposition in charge process.The cathode based on the optimized F doped carbon vesicle exhibits improved electrochemical performances including a low over-potential,large capacity and a long-term stability.Density functional theory (DFT) results show that F and C in C–F bond hasve a strong interaction to Li and O in Li_(2)O_(2),respectively,which can enhance the transfer of electrons from Li_(2)O_(2) to the carbon matrix to generate hole polaron and thus accelerate the delithiation and decomposition of Li_(2)O_(2).This work provides a new sight into understanding the mechanism of nucleation and decomposition of Li_(2)O_(2) for the development of high-performance Li-O_(2) batteries.展开更多
The construction of lithiophilic sites is an effective way to achieve uniform lithium(Li)ion deposition for stably cycling Li metal batteries.However,in-depth investigations involving lithiophilic sites denseness(LSD)...The construction of lithiophilic sites is an effective way to achieve uniform lithium(Li)ion deposition for stably cycling Li metal batteries.However,in-depth investigations involving lithiophilic sites denseness(LSD)in impacting Li ion deposition remain unknown.Herein we propose an insight into this issue by probing the effect of LSD on determining the Li ion deposition.Experimental characterization and theoretical simulation demonstrate that rational LSD plays a vital role in both Li nucleation and the subsequent Li ion plating behaviors.By tailoring the LSD from low to high,the accompanied Li nucleation overpotentials continuously decrease.Additionally,the Li ion mobility increases first and then weakens in the subsequent Li ion plating stage.Consequently,the Li metal with a moderate LSD allows a dendritefree morphology and satisfactory long-term cycling performances.This work affords a deeper fundamental understanding of lithiophilic chemistry that directs the development of efficient strategies to realize dendrite-free Li metal batteries.展开更多
Lithium–sulfur batteries have been attracting considerable research attention due to their high energy densities and low costs. However, one of their main challenges is the undesired shuttling of polysulfides, causin...Lithium–sulfur batteries have been attracting considerable research attention due to their high energy densities and low costs. However, one of their main challenges is the undesired shuttling of polysulfides, causing rapid capacity degradation. Herein, we report the first example of sulfiphilic VSe2 ultrafine nanocrystals immobilized on nitrogen-doped graphene to modify the battery separator for alleviating the shuttling problem. VSe2 nanocrystals provide numerous active sites for chemisorption of polysulfides as well as benefit the nucleation and growth of Li2S. Furthermore, the kinetic reactions are accelerated which is confirmed by higher exchange current density and higher lithium ion diffusion coefficient. And the first-principles calculations further show that the exposed sulfiphilic planes of VSe2 boost the redox of Li2S. When used as separators within the lithium sulfur batteries, the cell indicates greatly enhanced electrochemical performances with excellent long cycling stability and exceptional rate capability up to 8 C. Moreover, it delivers a higher areal capacity of 4.04 mAh·cm^−2 as well as superior cycling stability with sulfur areal loading up to 6.1 mg·cm^−2. The present strategy can encourage us in engineering novel multifunctional separators for energy-storage devices.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.21701145)the China Postdoctoral Science Foundation(Grant Nos.2017M610459,2018T110739)。
文摘Li-O_(2) batteries provide an attractive and potential strategy for energy conversion and storage with high specific energy densities.However,large over-potential in oxygen evolution reactions (OER) caused by the decomposition obstacles of Li_(2)O_(2) seriously impedes its electrochemical performances.Herein,a novel N,O,S and F co-doping vesicular carbon was prepared by self-template pyrolysis method and used in LiO_(2) battery to tune the nucleation and decomposition of Li_(2)O_(2).The introduction of F in the carbon matrix with suitable content can regulate the adsorption of intermediates,through which the morphology of Li_(2)O_(2) can be controlled to film,favorable to its decomposition in charge process.The cathode based on the optimized F doped carbon vesicle exhibits improved electrochemical performances including a low over-potential,large capacity and a long-term stability.Density functional theory (DFT) results show that F and C in C–F bond hasve a strong interaction to Li and O in Li_(2)O_(2),respectively,which can enhance the transfer of electrons from Li_(2)O_(2) to the carbon matrix to generate hole polaron and thus accelerate the delithiation and decomposition of Li_(2)O_(2).This work provides a new sight into understanding the mechanism of nucleation and decomposition of Li_(2)O_(2) for the development of high-performance Li-O_(2) batteries.
基金financial support from the projects of the National Natural Science Foundation of China(51972121,21671069)the Guangdong Basic and Applied Basic Research Foundation(2019A1515011502)the Guangdong Key Laboratory of Battery Safety(2019B121203008)。
文摘The construction of lithiophilic sites is an effective way to achieve uniform lithium(Li)ion deposition for stably cycling Li metal batteries.However,in-depth investigations involving lithiophilic sites denseness(LSD)in impacting Li ion deposition remain unknown.Herein we propose an insight into this issue by probing the effect of LSD on determining the Li ion deposition.Experimental characterization and theoretical simulation demonstrate that rational LSD plays a vital role in both Li nucleation and the subsequent Li ion plating behaviors.By tailoring the LSD from low to high,the accompanied Li nucleation overpotentials continuously decrease.Additionally,the Li ion mobility increases first and then weakens in the subsequent Li ion plating stage.Consequently,the Li metal with a moderate LSD allows a dendritefree morphology and satisfactory long-term cycling performances.This work affords a deeper fundamental understanding of lithiophilic chemistry that directs the development of efficient strategies to realize dendrite-free Li metal batteries.
基金The authors acknowledge the financial supports provided by the National Natural Science Foundation of China(Nos.21871164,21803036,and U1764258)the Taishan Scholar Project Foundation of Shandong Province(Nos.ts20190908 and ts201511004)the National Science Foundation of Shandong Province(No.ZR2019MB024).The theoretical calculations in this work were performed on the HPC Cloud Platform of Shandong University.We also thank Anhui Kemi Machinery Technology Co,Ltd for providing Teflon-lined stainless steel autoclave.
文摘Lithium–sulfur batteries have been attracting considerable research attention due to their high energy densities and low costs. However, one of their main challenges is the undesired shuttling of polysulfides, causing rapid capacity degradation. Herein, we report the first example of sulfiphilic VSe2 ultrafine nanocrystals immobilized on nitrogen-doped graphene to modify the battery separator for alleviating the shuttling problem. VSe2 nanocrystals provide numerous active sites for chemisorption of polysulfides as well as benefit the nucleation and growth of Li2S. Furthermore, the kinetic reactions are accelerated which is confirmed by higher exchange current density and higher lithium ion diffusion coefficient. And the first-principles calculations further show that the exposed sulfiphilic planes of VSe2 boost the redox of Li2S. When used as separators within the lithium sulfur batteries, the cell indicates greatly enhanced electrochemical performances with excellent long cycling stability and exceptional rate capability up to 8 C. Moreover, it delivers a higher areal capacity of 4.04 mAh·cm^−2 as well as superior cycling stability with sulfur areal loading up to 6.1 mg·cm^−2. The present strategy can encourage us in engineering novel multifunctional separators for energy-storage devices.