Probing Ionic Transport in a Lithiated Carbon Anode with Electrochemical Strain Microscopy

Lithium ion batteries are the most widely used energy storage device in both portable electronics and electric vehicles due to its high energy density. However, there are still remaining issues unsolved. To further improve the Li-ion battery performance, it’s important to understand the lithium ion intercalation/de-intercalation process upon cycling. The development of a new scanning probe microscopy technique (SPM), electrochemical strain microscopy (ESM), in which a combination of AC bias and DC bias is applied to the sample surface, allows us to evaluate mobile ionic diffusivity and electrochemical reactivity on the nanoscale.

In this work, we will first discuss about using a series of strain-based SPM techniques to distinguish different microscopic mechanisms including electromechanical coupling, spontaneous polarization, induced dipole moment and electrostatics. Then we will demonstrate the localized probing of lithium ion transport property in a lithiated carbon anode using ESM. Pristine carbon anode is also studied as comparison. Also, we’ll investigate the lithium ion transport through the solid electrolyte interface (SEI) layer, which is formed on the carbon anode surface upon cycling.