Magnetic resonance imaging (MRI) is a powerful technique that is non-invasive and non-destructive. We have extended the seminal use of Li-7 MRI from lithium dendrites in liquid-electrolyte-based batteries to visualize concentration gradients in polymer electrolytes for lithium batteries. Detecting both spatial gradients and temporal changes of salt concentration is powerful because it allows direct quantification of transport parameters, such as the diffusion coefficient. In this work, we discovered that lithium salt diffusion in polymer electrolyte is concentration dependent. (C) 2016 The Electrochemical Society. All rights reserved.