Scanning electrochemical cell microscopy for visualization and local electrochemical activities of lithium‐ion (de) intercalation process in lithium‐ion batteries electrodes

Abstract

Scanning electrochemical cell microscopy with a single barrel micro‐/nano‐pipette (SECCM) was applied to lithium iron phosphate (LiFePO4) composite positive electrodes and an isolated LiFePO4 secondary particle for lithium‐ion batteries. To analyze lithium‐ion (Li+) charge or discharge process on the electrodes using local probe, a pipette filled with LiCl electrolyte solution and Ag/AgCl quasi‐reference counter electrode (QRCE) was used. Both the local electrochemical activities of LiFePO4 on the composite electrodes and a single particle were revealed by SECCM as in‐situ direct measurement of current response‐related Li+ transport from mapping and cyclic voltammogram at confined area by the pipette. The mapping has visualized Li+ deintercalation process from LiFePO4 at +0.65 V (applied between the sample‐QRCE). We show that the SECCM system is a strong analytical tool for a characterization of local Li+ behavior of active electrode materials in lithium‐ion batteries.

Controlling Surface Contact, Oxygen Transport, and Pitting of Surface Oxide via Single-Channel Scanning Electrochemical Cell Microscopy

“…Since the substrate and electrolyte are often experimentally fixed, the magnitude of i trig is primarily controlled by E appr . For conductive substrates or electrolytes containing active redox species, such as carbon-based materials, , battery materials, ,− Au, ,, Pt, , Fc/Fc + , [Fe­(CN) 6 ] 2+/3+ , and [Ru­(NH 3 ) 6 ] 2+/3+ , , it is easy to achieve a i trig higher than the current threshold despite applying a small E appr . For example, an E appr of 0.65 V (vs Ag/AgCl) applied to a LiFePO 4 composite electrode gave rise to a i trig up to 9 pA (threshold = 2 pA) upon contact with a droplet cell at the end of a 100 nm diameter pipette .…”

Oil-Immersed Scanning Micropipette Contact Method Enabling Long-term Corrosion Mapping

“…The scanning micropipette contact method (SMCM, also called scanning electrochemical cell microscopy) − is a robust technique for direct high-resolution electrochemical activity mapping. The local electrochemical activities of electrocatalytic materials, − battery cathode materials, ,− polycrystalline electrodes, − graphite, − and other materials − with heterogeneous microstructural features have been successfully investigated using the SMCM. Compared to other scanning probe techniques, − the SMCM enables localized electrochemical measurements to be performed on a sample surface area of the scale of the micropipette size.…”

“…As a result, concentrated electrolyte solutions with high vapor pressure, although more realistic for a corrosion engineering testing purpose, are typically not used in SMCM experiments . In certain domains, such as SMCM studies of battery cathode materials, high concentrations of LiCl solutions ,, employed as electrolytes possess low evaporation rates. , For the same reason, the acid and alkaline electrolytes (HClO 4 , H 2 SO 4 , and KOH) ,,, used for the exploration of electrocatalytic materials do not suffer from the crystallization problem. In cases employing easily evaporating saline solutions, the concentrations are usually low, ,, thereby reducing the evaporation-related issues.…”

Scanning Electrochemical Cell Microscopy in a Glovebox: Structure‐Activity Correlations in the Early Stages of Solid‐Electrolyte Interphase Formation on Graphite

“…SECCM has proven powerful in studying structurally heterogeneous materials with practical relevance in many fields, including electrocatalysis, [42,43] corrosion [44] and sensing, [45] and its inherent features make it promising for battery electrode research. It has previously been employed to study the spatially-resolved activity and (de)lithiation of active materials used in positive battery electrodes such as LiFePO 4 composite electrodes, [46,47] isolated LiFePO 4 microparticles [47] and isolated LiMn 2 O 4 nanoparticles, where SECCM measurements were combined with identical location electron microscopy. [48] The above SECCM studies all made use of aqueous electrolytes; the use of nonaqueous solvents with low viscosity, as used in batteries, has been reported as challenging to implement with meniscus-based techniques; large droplet spread (surface wetting) has been observed.…”