Evolution of lithium clusters to superatomic Li3O+

Abstract

Accurate knowledge of the oxidation stages of lithium is crucially important for developing next-generation Li-air batteries. The intermediate oxidation stages, however, differ in the bulk and cluster forms of lithium. In this letter, using first-principles calculations, we predict several reaction pathways leading to the formation of Li 3 O + superatoms. Experimental results based on time-of-flight mass spectrometry and laser ablation of oxidized lithium bulk samples agreed well with our theoretical calculations. Additionally, the HOMO-LUMO gap of Li 3 O + was close to the energy released in one of these reaction paths, indicating that the superatom could act as a candidate charge-discharge unit.Keywords: Lithium-air battery, laser ablation, superatom, oxidized lithium, Li 3 O Lithium and its compounds are widely used in energy storage materials. Owing to their electrochemical properties, Li-based composites can act as both a good conductor and a semiconductor; switching of the conductivity can be realized by charging and discharging. For example semiconducting lithium peroxide 1 is composed of two equivalent lithium and oxygen atoms 2 . The formation of this compound is undesirable on the surface of lithium battery cathodes 3 ; however, Li 2 O 2 composites plays a key role in large volume Li-air batteries 3-8 . The charge-discharge pathways of Li 2 O 2 have been extensively studied in the determination of suitable battery electrolytes 3,6,8 . To further enlarge the charge-to-mass ratio of batteries, nano-and sub-nano-scale charge carriers are considered to be more capable candidates than their bulk counterparts 9,10 . In contrast to the numerous studies of Li 2 O 2 in the bulk phase, investigations of free Li-O clusters have mainly focused on hyper-lithiated Li 3 O (0,±) clusters. This set of clusters is of particular interest owing to its excess valence electrons. These clusters have been termed "superalkali atoms" in their neutral or charged forms [11][12][13][14] . Although the structure and properties of Li 3 O clusters have been systematically investigated 15 , their formation processes are not yet fully understood. Furthermore, despite many early studies on the thermochemical properties of free Li-O clusters by mass spectrometry 16 , there has been no physical characterization of lithium bulk oxidation states and those of corresponding cluster formations. As building blocks of many nanomaterials with special functionalities 17,18 , Li-based a) E-mail: henri.pauna@oulu.fi b) E-mail: mzhang@ecust.edu.cn clusters also possess unique properties, which could be applied to Li-air batteries 7 . Thus, studies of the formation mechanisms and transformations between Li-O clusters might provide new insights into future energy storage materials.In this letter we report on the evolution and transformation of free lithium clusters to superatomic Li 3 O + . The stability and reaction pathways of Li 3 O + are predicted by first-principles calculations and supported by time-of-flight mass spectrometry (TOFMS) experiments...

Chemical properties of superatomic Li3O clusters from a density functional theory perspective: formation of chloride and adsorption behavior on graphynes

“…Hence, the superatom Li 3 O is highly stable and can be assembled easily, consistent with our previous experimental findings based on time-of-flight mass spectrometry. 37 …”

“…Among the studied superatoms, the structure and properties of superalkali atom Li 3 O in its neutral or charged form have been systematically investigated. [33][34][35][36] In our previous work, 37 the predicted Li 3 O + has been identified in the gas form. Its formation process has been proposed and the possibility of application as a building unit for energy storage has been uncovered.…”

“…Hence, the superatom Li 3 O is highly stable and can be assembled easily, consistent with our previous experimental findings based on time-of-flight mass spectrometry. 37 Next, the molecular orbitals of (Li 3 O)Cl and the corresponding NaCl are investigated and shown in Fig. 3.…”

First‐principles studies of lithium adsorption and diffusion on silicene with grain boundaries

“…However, future batteries require smaller LIB dimensions, lighter weights, along with higher energy densities. To meet these stringent requirements, extensive researches have been emphasized on explorations of the advanced electrode materials which can provide high charge capacity, long cyclic stability, high‐rate capability, and safety . Graphene and oxidized graphene have been found with higher capacities of 600 to 1000 mAh/g than the bulk counterpart of graphite (372 mAh/g) .…”