Lithiation of Single-Crystalline Ge(111) and Si(111) Investigated by X-ray Photoelectron Spectroscopy

Abstract

Silicon and germanium are considered as very promising anode materials for lithium-ion batteries due to their high capacities. Understanding the lithiation mechanisms of Si and Ge is important to overcome problems, such as volume expansion, with such materials. In this paper, the changes in the chemical state and the local structure of single-crystalline Si(111) and Ge(111) during the lithiation process on an atomic scale were studied by X-ray photoelectron spectroscopy (XPS). Remarkable differences in the lithiation process between Si(111) and Ge(111) were observed. Two Si 2p peaks in the XPS were observed during the lithiation of Si(111), which can be assigned to the elemental Si 2p and Li x Si alloying Si 2p. In contrast, Ge(111) shows one peak in the Ge 3d regime and the peak gradually reduces in intensity and shifts to lower binding energy upon lithiation. Our results also indicate that ∼SiLi3.0 was formed at the surface and metallic Li was more likely to accumulate on the surface of Si(111), even though elemental Si was still available. Nevertheless, Ge(111) shows a homogeneous phase upon lithiation, and different intermediate phases, such as GeLi0.9, GeLi1.5, GeLi3.6, are present with the increase in Li. We expect that our understanding of the lithiation process could contribute to the development of the next-generation high-performance Si- and Ge-based anodes.

Electrochemical Lithiation and Delithiation in Amorphous Si Thin Film Electrodes Studied by Operando X-ray Photoelectron Spectroscopy

“…X-ray photoelectron spectroscopy (XPS) is a powerful tool for analyzing the composition of reaction products, chemical states, and electronic structure in electrode materials. − In our previous study, the chemical states of an amorphous Si thin-film electrode sputter-deposited on a Li 6.6 La 3 Zr 1.6 Ta 0.4 O 12 (LLZT) solid electrolyte after the first lithiation and successive delithiation steps were quantitatively analyzed by electrochemical techniques coupled with XPS . In addition to the lithium silicide (Li x Si) quasi-reversibly responding to the lithiation/delithiation, a few irreversible species such as Li 2 O, Li 2 CO 3 , and lithium silicates (Li silicates) were formed due to the side reactions of Li x Si with residual gases and lithiation of Si native oxides.…”

Facile synthesis of Si/Ge/graphite@C composite with improved tap density and electrochemical performance

“…S2a and b† are the surface oxidation of Si and Ge, respectively. 38,39 The peak of Si–Si (Si 0 : 99.3 eV) is not apparent, which may be due to the surface oxidation of the sample. The two peaks at around 29.76 and 31.69 eV of Ge 3d spectrum in Fig.…”

Development of a Smart and Ultrafast Flexible Humidity Sensor Using the 0D/2D Au/GeS Heterostructure for Human Respiration Rate Monitoring

“…On the other hand, Figure c represents the XPS result of the heterostructure. Same peaks were seen at 1248 and 1217 eV for the Ge 2p 1/2 and Ge 2p 3/2 , respectively (Figure d) . Additional peaks for Ge could also be detected at 128.5, 124, 32.8, 31.6, and 29.9 eV, which were assigned as Ge 3p 1/2 , Ge 3p 3/2 , and Ge 3d (Ge 3+ , Ge 2+ , and Ge 0+ ) signals, respectively (Figure e,f). , The germanium centers in GeS have a tendency to undergo oxidation.…”