Atomic‐Scale Monitoring of Electrode Materials in Lithium‐Ion Batteries using In Situ Transmission Electron Microscopy

Abstract

Lithium‐ion batteries (LIBs) are energy storage devices that have received much attention because of their high energy density, high power capacity, and long lifetime. However, even though they are used widely in daily life, their cycling life and safety need further improvement. Understanding the reaction mechanisms and the structural degradation during the lithiation/delithiation process is a prerequisite to further improve the performance of LIBs. In situ transmission electron microscopy (TEM) allows one to monitor structural evolution at the atomic scale in real time, thus providing an unprecedented opportunity to characterize the lithiation reaction pathway in a nonequilibrium state during battery cycling. In this article, the recent advances with respect to elucidating the relationships of dynamic structural evolution, reaction kinetics, and performance of different nanostructured electrode materials at the atomic scale using in situ TEM, based on three representative reaction mechanisms, are described. Specifically, the three systems are intercalation reaction, conversion reaction, and alloying reaction. Based on the advances that have been made, it is expected that in situ TEM will play an indispensable role on future design of LIBs electrode materials.

Interface charges boosted ultrafast lithiation in Li4Ti5O12 revealed by in-situ electron holography

“…[24] . Recently, it has been successfully applied to monitor charge distribution and interfacial electric potential within the LiCoO 2 all-solid-state battery lamella [25] and Ge nanowire anode [22] in the field of rechargeable batteries [26] .…”

Revealing the Atomic Origin of Heterogeneous Li‐Ion Diffusion by Probing Na

“…Its reversibility and the governing kinetics dictate many of the battery performance parameters such as cycling stability and rate capability . However, it is challenging to understand the ion diffusion process at the atomic level for manipulation in practical rechargeable batteries . One major barrier is the pervasive structural defects and material heterogeneities including compositional and morphological nonuniformities .…”

“…Transmission electron microscopy (TEM) is a powerful tool to characterize the structural and chemical information of materials with a resolution down to sub‐Å level. Recently, advanced TEM characterization including cryo‐TEM and in situ techniques have been applied on the study of structural evolution and ion transfer process in operando of battery materials . However, plagued by the light weight of Li, direct visualizing it in the transition metal (TM) oxide matrix is still challenging, particularly at atomic level .…”

Alloying of Alkali Metals with Tellurene

“…In-situ TEM has proved to be successful in understanding the major electrochemical mechanisms [34][35] (i.e., intercalation, alloying, and conversion) that an anode material could undergo during ion insertion/extraction. Especially for alloying/de-alloying reactions, in-situ TEM provides useful information related to volume expansion, change in morphology, and change in crystallinity that the alloying material undergoes 34 .…”

“…In-situ TEM has proved to be successful in understanding the major electrochemical mechanisms [34][35] (i.e., intercalation, alloying, and conversion) that an anode material could undergo during ion insertion/extraction. Especially for alloying/de-alloying reactions, in-situ TEM provides useful information related to volume expansion, change in morphology, and change in crystallinity that the alloying material undergoes 34 . In this work, we used in-situ TEM to study the alloying of Te with Li, Na as well as K. Figure S2 shows a schematic of the in-situ TEM setup used to study the alkalization (lithiation/sodiation/potassiation) of fewlayer Te, wherein the corresponding alkali metal (Li/Na/K) was used as the counter electrode, naturally grown metal oxide layer (i.e., lithium oxide, sodium oxide or potassium oxide) as a solid-state electrolyte, and Te as the working electrode with gold (Au) or tungsten (W) as the current collectors.…”