Operando surface science methodology reveals surface effect in charge storage electrodes

Abstract

Surface and interface play critical roles in energy storage devices, calling for operando characterization techniques to probe the electrified surfaces/interfaces. In this work, surface science methodology including electron spectroscopy and scanning probe microscopy has been successfully applied to visualize electrochemical processes at operating electrode surfaces in an Al/graphite model battery. Intercalation of anions together with cations is directly observed in surface region of the graphite electrode with tens of nanometers thickness, whose concentration is amazingly one order higher than that in bulk. An intercalation pseudocapacitance mechanism and a double specific capacity in the electrode surface region are expected based on the super-dense intercalants and anion/cation co-intercalation, which are in sharp contrast with the battery-like mechanism in the electrode bulk. The distinct electrochemical mechanism at electrode surface is well verified by performance tests of real battery devices, showing that surface-dominant nanometer thick graphite cathode outperforms bulk-dominant micrometer thick graphite cathode. Our findings highlight the important surface effect of working electrodes in charge storage systems.

Nonaqueous Rechargeable Aluminum Batteries: Progresses, Challenges, and Perspectives

“…Furthermore, PG presented an elevated volumetric change upon cycling. Wang et al recently observed the direct diffusion process of the intercalated ions underneath the highly ordered pyrolytic graphite (HOPG) surface by real-time optical microscopy, confirming more than 5-fold volume expansion by in situ atomic force microscopy (AFM) analysis …”

“…Wang et al recently observed the direct diffusion process of the intercalated ions underneath the highly ordered pyrolytic graphite (HOPG) surface by real-time optical microscopy, confirming more than 5-fold volume expansion by in situ atomic force microscopy (AFM) analysis. 246 Song's group recently observed the thickness change of CoB/ few-layer graphene (FLG) composite positive electrodes during cycling by in situ SEM technology, which would provide an effective strategy for addressing the unexpected volume expansion, as shown in Figure 17. 110 It was observed that FLG presented huge volume expansion (50%) during charge and discharge, while the expansion of CoB and composite positive electrode was 5% and 10%, respectively.…”

“…The similar in situ Raman results were observed in the anion intercalation/deintercalation processes of graphite from Dai’s and Gao’s previous work. ,, Recently, a different intercalation pseudocapacitance mechanism in the HOPG surface was proposed through operando Raman and X-ray photoelectron spectroscopy (XPS) characterizations. The results presented abnormal superdense intercalant state, forming multilayered cations/anions cointercalation in the graphene layers …”

In Situ Visualization of Atmosphere-Dependent Relaxation and Failure in Energy Storage Electrodes

“…Operando XPS has been performed upon charging the planar model battery in an ultrahigh vacuum (UHV) XPS chamber (Figure S14), and the intensities of XPS Al 2p, Cl 2p, and N 1s signals increase but that of C 1s decreases (Figure S15). The binding energies (BEs) of the intercalants are all ∼1.7 eV lower than the surface absorption species due to the change in the surface work function …”

“…33,34 Considering the significant role of the atmosphere in ESDs, it is important to investigate atmosphere-dependent battery behaviors through operando/in situ characterization methodology. In this work, as exemplified by planar model aluminum ion battery (AIB) devices, 35,36 atmosphere-dependent relaxation and failure processes of the devices have been comprehensively studied by in situ Raman, XRD and X-ray photoelectron spectroscopy (XPS) within corresponding atmosphere-controlled characterization cells. In anhydrous atmospheres, the relaxation effects of the working graphite intercalation compound (GIC) electrodes are manifested by the GIC stage-structure change as well as electronic relaxation caused by ion redistribution.…”