In situ observation of the electrochemical behavior of Li–CO_(2)/O_(2)batteries in an environmental transmission electron microscope

Li–CO_(2)/O_(2)batteries,a promising energy storage technology,not only provide ultrahigh discharge capacity but also capture CO_(2)and turn it into renewable energy.Their electrochemical reaction pathways'ambiguity,however,creates a hurdle for their practical application.This study used copper selenide(CuSe)nanosheets as the air cathode medium in an environmental transmission electron microscope to in situ study Li–CO_(2)/O_(2)(mix CO_(2)as well as O_(2)at a volume ratio of 1:1)and Li–O_(2)batteries as well as Li–CO_(2)batteries.Primary discharge reactions take place successively in the Li–CO_(2)/O_(2)–CuSe nanobattery:(I)4Li^(+)+O_(2)+4e^(−)→2Li_(2)O;(II)Li_(2)O+CO_(2)→Li_(2)CO_(3).The charge reaction proceeded via(III)2Li_(2)CO_(3)→4Li^(+)+2CO_(2)+O_(2)+4e^(−).However,Li–O_(2)and Li–CO_(2)nanobatteries showed poor cycling stability,suggesting the difficulty in the direct decomposition of the discharge product.The fluctuations of the Li–CO_(2)/O_(2)battery's electrochemistry were also shown to depend heavily on O_(2).The CuSe‐based Li–CO_(2)/O_(2)battery showed exceptional electrochemical performance.The Li^–CO_(2)/O_(2)battery offered a discharge capacity apex of 15,492 mAh g^(−1) and stable cycling 60 times at 100 mA g^(−1).Our research offers crucial insight into the electrochemical behavior of Li–CO_(2)/O_(2),Li–O_(2),and Li–CO_(2)nanobatteries,which may help the creation of high‐performance Li–CO_(2)/O_(2)batteries for energy storage applications.

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.

In-situ imaging electrocatalysis in a solid-state Li-O_(2) battery with CuSe nanosheets as air cathode

The development of highly efficient catalysts in the cathodes of rechargeable Li-O_(2) batteries is a considerable challenge.To enhance the electrochemical performance of the Li-O_(2) battery,it is essential to choose a suitable catalyst material.Copper selenide(CuSe)is considered as a more promising cathode catalyst material for Li-O_(2) battery due to its better conductivity and rich electrochemical active sites.However,its electrochemical reaction and fundamental catalytic mechanism remain unclear till now.Herein,in-situ environmental transmission electron microscopy technique was used to study the catalysis mechanism of the CuSe nanosheets in Li-O_(2) batteries during discharge and charge processes.It is found that Li_(2)O was formed and decomposed around the ultrafine-grained Cu during the discharge and charge processes,respectively,demonstrating excellent cycling.This indicate that the freshly formed ultrafine-grained Cu in the conversion reaction catalyzed the latter four-electron-transfer oxygen reduction reaction,leading to the formation of Li_(2)O.Our study provides important understanding of the electrochemistry of the LiO_(2) nanobatteries,which will aid the development of high-performance Li-O_(2) batteries for energy storage applications.

In situ observation of cracking and self-healing of solid electrolyte interphases during lithium deposition

The growth of lithium(Li)whiskers is detrimental to Li batteries.However,it remains a challenge to directly track Li whisker growth.Here we report in situ observations of electrochemically induced Li deposition under a CO_(2) atmosphere inside an environmental transmission electron microscope.We find that the morphology of individual Li deposits is strongly influenced by the competing processes of cracking and self-healing of the solid electrolyte interphase(SEI).When cracking overwhelms self-healing,the directional growth of Li whiskers predominates.In contrast,when self-healing dominates over cracking,the isotropic growth of round Li particles prevails.The Li deposition rate and SEI constituent can be tuned to control the Li morphologies.We reveal a new“weak-spot”mode of Li dendrite growth,which is attributed to the operation of the Bardeen-Herring growth mechanism in the whisker’s cross section.This work has implications for the control of Li dendrite growth in Li batteries.