In situ Observation of Li Deposition-Induced Cracking in Garnet Solid Electrolytes

Lithium(Li)penetration through solid electrolytes(SEs)induces short circuits in Li solid-state batteries(SSBs),which is a critical issue that hinders the development of high energy density SSBs.While cracking in ceramic SEs has been often shown to accompany Li penetration,the interplay between Li deposition and cracking remains elusive.Here,we constructed a mesoscale SSB inside a focused ion beam-scanning electron microscope(FIB-SEM)for in situ observation of Li deposition-induced cracking in SEs at nanometer resolution.Our results revealed that Li propagated predominantly along transgranular cracks in a garnet Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)(LLZTO).Cracks appeared to initiate from the interior of LLZTO beneath the electrode surface and then propagated by curving toward the LLZTO surface.The resulting bowl-shaped cracks resemble those from hydraulic fracture caused by high fluid pressure on the surface of internal cracks,suggesting that the Li deposition-induced pressure is the major driving force of crack initiation and propagation.The high pressure generated by Li deposition is further supported by in situ observation of the flow of filled Li between the crack flanks,causing crack widening and propagation.This work unveils the dynamic interplay between Li deposition and cracking in SEs and provides insight into the mitigation of Li dendrite penetration in SSBs.

Revealing alkali metal ions transport mechanism in the atomic channels of Au@a-MnO_(2)

Understanding alkali metal ions’(e.g.,Li^(+)/Na^(+)/K^(+))transport mechanism is challenging but critical to improving the performance of alkali metal batteries.Herein using a-MnO_(2)nanowires as cathodes,the transport kinetics of Li^(+)/Na^(+)/K^(+)in the 2×2 channels of a-MnO_(2)with a growth direction of[001]is revealed.We show that ion radius plays a decisive role in determining the ion transport and electrochemistry.Regardless of the ion radii,Li^(+)/Na^(+)/K^(+)can all go through the 2×2 channels of a-MnO_(2),generating large stress and causing channel merging or opening.However,smaller ions such as Li^(+)and Na^(+)cannot only transport along the[001]direction but also migrate along the<110>direction to the nanowire surface;for large ion such as K^(+),diffusion along the<110>direction is prohibited.The different ion transport behavior has grand consequences in the electrochemistry of metal oxygen batteries(MOBs).For Li-O_(2)battery,Li^(+)transports uniformly to the nanowire surface,forming a uniform layer of oxide;Na^(+)also transports to the nanowire surface but may be clogged locally due to its larger radius,therefore sporadic pearl-like oxides form on the nanowire surface;K^(+)cannot transport to the nanowire surface due to its large radius,instead,it breaks the nanowire locally,causing local deposition of potassium oxides.The study provides atomic scale understanding of the alkali metal ion transport mechanism which may be harnessed to improve the performance of MOBs.

The proximity between hydroxyl and single atom determines the catalytic reactivity of Rh1/CeO_(2) single-atom catalysts

The local structure of the metal single-atom site is closely related to the catalytic activity of metal single-atom catalysts(SACs).However,constructing SACs with homogeneous metal active sites is a challenge due to the surface heterogeneity of the conventional support.Herein,we prepared two Rh1/CeO_(2)SACs(0.5Rh1/r-CeO_(2)and 0.5Rh1/c-CeO_(2),respectively)using two shaped CeO_(2)(rod and cube)exposing different facets,i.e.,CeO_(2)(111)and CeO_(2)(100).In CO oxidation reaction,the T100 of 0.5Rh1/r-CeO_(2)SACs is 120°C,while the T100 of 0.5Rh1/c-CeO_(2)SACs is as high as 200°C.Via in-situ CO diffuse reflectance infrared Fourier transform spectroscopy(CO-DRIFTS),we found that the proximity between OH group and Rh single atom on the plane surface plays an important role in the catalytic activity of Rh1/CeO_(2)SAC system in CO oxidation.The Rh single atom trapped at the CeO_(2)(111)crystal surface forms the Rh1(OH)adjacent species,which is not found on the CeO_(2)(100)crystal surface at room temperature.Furthermore,during CO oxidation,the OH group far from Rh single atom on the 0.5Rh1/c-CeO_(2)disappears and forms Rh1(OH)adjacent species when the temperature is above 150°C.The formation of Rh1(OH)adjacentCO intermediate in the reaction is pivotal for the excellent catalytic activity,which explains the difference in the catalytic activity of Rh single atoms on two different CeO_(2)planes.The formed Rh1(OH)adjacent-O-Ce structure exhibits good stability in the reducing atmosphere,maintaining the Rh atomic dispersion after CO oxidation even when pre-reduced at high temperature of 500°C.Density functional theory(DFT)calculations validate the unique activity and reaction path of the intermediate Rh1(OH)adjacentCO species formed.This work demonstrates that the proximity between metal single atom and hydroxyl can determine the formation of active intermediates to affect the catalytic performances in catalysis.

锂沉积过程中固体电解质间相开裂与自愈合的原位观察

锂金属电池由于其超高的理论容量,被誉为是电池的"圣杯".然而,锂金属电池循环过程中树枝状或苔藓状锂的生长会使电池容量下降、电解液消耗、内部短路甚至起火爆炸.而直接追踪锂枝晶的生长仍然是一个巨大的挑战.本文报道了在CO_(2)气氛下利用环境电镜实时地观察了电化学诱导的锂沉积.研究发现单个锂沉积的形态强烈地受到固体电解质界面(SEI)开裂和自愈合的竞争过程的影响.当SEI膜的开裂速度超过自愈合时,锂晶须的定向生长占主导地位.相反地,当自愈大于裂纹时,圆形锂颗粒的各向同性生长将占主导地位.并且当SEI层是Li2O时,锂沉积的形貌只有球形,没有晶须的生成.因此,可以通过调节锂沉积速率和SEI成分来控制锂的形貌.本文还揭示了锂枝晶生长的一种新的"弱点"模式,这主要是由于在晶须截面上的Bardeen-Herring生长机制的作用.本研究对控制锂电池中锂枝晶的生长具有重要意义.

Phylogeny of drepanosiphine aphids sensu lato(Hemiptera,Aphidoidea)inferred from molecular and morphological data

As the second largest and most diverse group in the superfamily Aphidoidea,the phylogeny of drepanosiphine aphids sensu lato(s.l.)is critical for discussing the evolution of aphids.However,the taxa composition and phylogenetic relationships of drepanosiphine aphids s.l.have not been fully elucidated to date.In this study,based on total-evidence analyses combining 4 molecular genes(3 mitochondrial,COI,tRNA-Leu/COII,and CytB;1 nuclear,EF-1A)and 64 morphological and biological characteristics,the phylogeny of this group was reconstructed for the first time at the subfamily level using different datasets,parsimonies and model-based methods.All of our phylogenetic inferences clearly indicated that the drepanosiphine aphids s.l.was not a monophyletic group and seemed to support the division of the drepanosiphine aphids s.l.into different groups classified at the subfamily level.Calaphidinae was also not a monophyletic group,and Saltusaphidinae was nested within this subfamily.Drepanosiphinae was not clustered with Chaitophorinae,which was inconsistent with the previous hypothesis of a close relationship between them,illustrating that their phylogeny remains controversial.Overall,some groups of drepanosiphine aphids s.l.,including Phyllaphidinae,Macropodaphidinae,Pterastheniinae,Lizeriinae,Drepanosiphinae,Spicaphidinae,Saltusaphidinae,and Calaphidinae,clustered together and might constitute the actual drepanosiphine aphids s.l.To a certain extent,our results clarified the phylogenetic relationships among drepanosiphine aphids s.l.and confirmed their taxonomic status as subfamilies.