Effect of Substrate Permeability on Scanning Ion Conductance Microscopy: Uncertainty in Tip–Substrate Separation and Determination of Ionic Conductivity

Abstract

Composite electrodes can significantly improve the performance of an electrochemical device by maximizing surface area and active material loading. Typically, additives such as carbon are used to improve conductivity and a polymer is used as a binder, leading to a heterogeneous surface film with thickness on the order of 10s of micrometers. For such composite electrodes, good ionic conduction within the film is critical to capitalize on the increased loading of active material and surface area. Ionic conductivity within a film can be tricky to measure directly, and homogenization models based on porosity are often used as a proxy. SICM has traditionally been a topography-mapping microscopy method for which we here outline a new function and demonstrate its capacity for measuring ion conductivity within a lithium-ion battery film.

Charge Storage in Graphene Oxide: Impact of the Cation on Ion Permeability and Interfacial Capacitance

“…Alternatively, scanning ion conductance microscopy (SICM) is an electrochemical scanning probe technique (Figure b) traditionally employed as a surface topography mapping tool but has also seen applied in surface charging and ion flux imaging . SICM has been employed to probe ion transport through membranes, and due to the high lateral resolution, much of its application has focused on the transport of local conductivity on the nanoscale, mainly through single pores − and cells. − Recently, we demonstrated the determination of bulk ionic conductivity, independently of electrical conductivity in a permeable lithium ion battery cathode through fitting SICM approach curves to numerical simulations . Herein we describe the investigation of ion permeability (ε) within GO, demonstrating the influence of surface charge on different cations with SICM.…”

Scanning ion conductance microscopy reveals differences in the ionic environments of gram positive and negative bacteria

“…Modifying the cell wall thickness within the range observed by EM ( Figure S-13B) causes only minor changes in the simulated normalized currents, because the perturbation caused by the SICM probe only extends into the outermost region of the cell wall ( Figure 8B), as also seen with permeable abiotic substrates. 34 An interesting avenue for future exploration would be to analyze in more detail the current-time transients in pulsed-potential measurements, and apply double pulses, to transiently drive the cell wall (substrate)-interface out of equilibrium with SICM, and monitor its return to equilibrium. Analysis of similar scanning electrochemical microscopy studies has enabled the relative diffusion coefficient and partition coefficient to be determined independently in a single measurement, without the tip contacting the sample.…”

“…33 AFM is only sensitive to the charge environment of the outermost surface, whereas with SICM there is the possibility of probing ion permeability of a sample. 4,34 Furthermore, for non-invasive scanning of soft biological samples, SICM avoids deformation of the sample surface and consequently can provide better spatial resolution and longer viable experiment time scale. 35,36 Here, we use SICM to map the charge environment of two different bacterial species,…”

Local probe investigation of electrocatalytic activity

“… 78 Besides topography measurements, SICM has also found utility in the determination of ion conductivity. 79 Very recently a development has been made, where SICM can be used for generating local electrochemical impedance spectra, in which case the local capacitance and topography can be determined separately in one measurement. 80 It's worth mentioning that the possibility of non-contact imaging with SICM allows the investigation of fragile samples that otherwise are investigated with difficulty by AFM for example.…”