a method and system for probing mobile ion diffusivity and electrochemical reactivity on a nanometer length scale of a free electrochemically active surface includes a control module that biases the surface of the material . an electrical excitation signal is applied to the material and induces the movement of mobile ions . an spm probe in contact with the surface of the material detects the displacement of mobile ions at the surface of the material . a detector measures an electromechanical strain response at the surface of the material based on the movement and reactions of the mobile ions . the use of an spm tip to detect local deformations allows highly reproducible measurements in an ambient environment without visible changes in surface structure . the measurements illustrate effective spatial resolution comparable with defect spacing and well below characteristic grain sizes of the material .