Synchrotron X‐Ray Absorption Spectroscopy and Electrochemical Study of Bi₂O₂Se Electrode for Lithium‐/Potassium‐Ion Storage

Abstract

The increasing demand from portable electronics, electric vehicles, and renewable energy storage/conversion has created great opportunities for developing high-performance and scalable energy storage systems. [1] Potassium-ion batteries (PIBs) that are attractive for abundant potassium resources and low standard reduction potential (−2.93 V vs K + /K) can be a promising alternative energy storage system for lithium-ion batteries (LIBs) whose lithium resources are currently limited by the high market price. [2,3] Understanding the fundamental electrochemical mechanisms during battery operation is critically important for expediting battery industrial upgrade. State-of-the-art characterization techniques, including in situ/ operando X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM), were conducted to probe crystalline structure changes, redox reactions, and cell degradation mechanisms of rechargeable batteries during charging/discharging. [4] Electrochemical reaction mechanisms of alloying-type and conversiontype anodes have been extensively studied in the past decades, and great progress has been made by virtue of these advanced characterization techniques. For example, the phase change process of Sb 2 Se 3 for sodium-ion batteries was investigated by in situ synchrotron XRD, showing that the Sb 2 Se 3 electrode underwent a typical insertion-conversion-alloying process upon discharge. Specifically speaking, during the initial discharge process, Na + was inserted into the Sb 2 Se 3 interlayer to form Na x Sb 2 Se 3 intermediate beyond 1.1 V, then Sb 3+ was displaced by Na + to form metallic Sb and Na 2 Se through a conversion reaction between 1.1 and 0.6 V, and metallic Sb was further alloyed with Na + through multistep alloying reactions to form Na 3 Sb end-phase. [5] Furthermore, the electrochemical reaction process of SnO 2 for lithium-ion storage was investigated by in situ synchrotron XRD, in situ synchrotron XAS, and in situ TEM. At the start of discharge, metallic Sn and Li 2 O were generated through the conversion reaction between SnO 2 and Li. Then, Sn was lithiated into amorphous Li x Sn intermediates and Li 4.4 Sn end-phase by multistep alloying reactions. [6] Recently, Elucidating the battery operating mechanism is important for designing better conversion-type anodes as it determines the strategies used to improve electrochemical performances. Herein, the authors pioneered the electrochemical study of layered Bi 2 O 2 Se as anodes for lithium-ion batteries (LIBs) and potassium-ion batteries (PIBs). Surprisingly, the Bi 2 O 2 Se/ graphite composite electrode shows even better cycle stability for PIBs. The electrochemical reaction mechanisms of the Bi 2 O 2 Se/graphite electrode for LIBs and PIBs are investigated by potential-resolved in situ and ex situ X-ray absorption spectroscopy based at the Bi L III -edge and Se K-edge through characterizing the local atomic structure evolution, valence state change, and charge transfer. New insights are gai...

In‐Depth Mechanism Understanding for Potassium‐Ion Batteries by Electroanalytical Methods and Advanced In Situ Characterization Techniques

“…A remarkable example for PIBs is the work of Guo's group. [97] They probed the potassium/lithium storage mechanism of conversion-type Bi Generally speaking, the edge absorption spectrum has a higher correlation with the height of the white peak or the absorption area. [98] Similarly, the valence state of Se is indicated as divalent by Se K-edge XANES.…”

“…A remarkable example for PIBs is the work of Guo's group. [ 97 ] They probed the potassium/lithium storage mechanism of conversion‐type Bi 2 O 2 Se/graphite (Bi 2 O 2 Se/G) anode and found that its potassium storage was superior to lithium storage. The redox reactions, charge transfer process and local atomic structure changes were also unveiled through in situ XAS.…”

In Situ Synchrotron X‐Ray Absorption Spectroscopy Studies of Anode Materials for Rechargeable Batteries

“…Bi 2 O 2 Se was investigated as advanced anodes for lithium‐ion batteries and potassium‐ion batteries, and the mechanism were studied by in situ Bi L III ‐edge and Se K‐edge XAS. revealing an insertion‐conversion‐alloying process upon lithiation and the dissolution of Li−Se intermediate phases in the electrolyte [67] …”

“…revealing an insertionconversion-alloying process upon lithiation and the dissolution of LiÀ Se intermediate phases in the electrolyte. [67]…”

Updated Insights into 3D Architecture Electrodes for Micropower Sources

“…Such information will be highly valuable as it will reveal the evolution of 3D architecture electrodes during electrochemical processes and elucidate their electrode degradation mechanisms. [ 119–125 ] Thus, these advanced characterization results will guide further optimization of 3D architecture electrodes. Currently, a single structural unit of a 3D architecture electrode is typically selected as the research subject of an in situ microscopy characterization.…”