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Electrochemistry of Dual-Ion Systems: Probing Nanoscale Dynamics

Researchers investigated the electrochemical dynamics of a model dual-ion material using AFM techniques. The nanoscale measurements allowed them to separate the contributions of competing relaxation processes and determine values for local diffusivity and activation energy.

(left) Schematics of AFM experimental setup and soda-lime float glass microstructure; (middle) graphs of applied DC bias voltage and resulting system response; relaxation curves and their decomposition into faster and slower processes.Dual-ion batteries, which use both anions and cations in the charge-discharge process, have exciting potential for electric vehicles, grid-scale storage, and other energy technology. However, a deeper understanding of electrochemical conversion processes in multiple-ion systems is needed to turn this potential into reality.

A team led by researchers at Xiangtan University used AFM tools to resolve the dynamics of dual-ion systems on the nanoscale. Through measurements of local electrochemical strain relaxation on soda-lime float glass, they decoupled two competing effects: a faster process arising from Vegard strain and a slower process from electrochemical dipoles. By varying the measurement temperature they also determined values for the local diffusion coefficient D and activation energy.

The results demonstrate a powerful tool for evaluating ion dynamics on the nanoscale that could prove valuable in a wide range of energy storage and conversion applications.

Relaxation behavior measured at 55, 75, and 100 C; time constants versus temperature for faster and slower relaxation processes; plot of D versus inverse temperature to obtain activation energy.


Instruments used

Cypher ES and MFP-3D BIO

Techniques used

Strain relaxation measurements of nanometer-scale volumes were made using electrochemical strain microscopy (ESM) on a Cypher ES AFM under nitrogen flow. The sample was electrically grounded and a positive or negative bias voltage applied to the tip of a conductive cantilever. As these data suggest, the ESM option for Asylum AFMs provides unprecedented resolution for electrochemical studies. Temperature-dependent measurements were straightforward to set up and perform using the built-in heating stage of the Cypher ES, which provides precise temperature control up to 250 °C. Additional experiments to compare the first and second harmonic components of the ESM signal (not shown here) were performed on an MFP-3D BIO AFM in ambient conditions.


Citation: J. Yu, B. Huang, A. Li et al., Resolving local dynamics of dual ions at the nanoscale in electrochemically active materials. Nano Energy 66, 104160 (2019).

Note: The data shown here are reused under fair use from the original article, which can be accessed through the article link above.


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