A parallel-plate RF probe and battery cartridge for 7Li ion battery studies

Abstract

A new parallel-plate resonator for ⁷Li ion cell studies is introduced along with a removable cartridge-like electrochemical cell for lithium ion battery studies. This geometry separates the RF probe from the electrochemical cell permitting charge/discharge of the cell outside the magnet and introduces the possibility of multiplexing samples under test. The new cell has a geometry that is similar to that of a real battery, unlike the majority of cells employed for MR/MRI studies to this point. The cell, with electrodes parallel to the B₁ magnetic field of the probe, avoids RF attenuation during excitation/reception. The cell and RF probe dramatically increase the sample volume compared to traditional MR compatible battery designs. Ex situ and in situ 1D ⁷Li profiles of Li ions in the electrolyte solution of a cartridge-like cell were acquired, with a nominal resolution of 35 µm at 38 MHz. The cell and RF probe may be employed for spectroscopy, imaging and relaxation studies. We also report the results of a T₁-T₂ relaxation correlation experiment on both a pristine and fully charged cell. This study represents the first T₁-T₂ relaxation correlation experiment performed in a Li ion cell. The T₁-T₂ correlation maps suggest lithium intercalated into graphite is detected by this methodology in addition to other Li species.

Keywords: Ex situ; In operando; In situ; Lithium intercalation; Lithium-ion battery; MRI; Optimization; Parallel-plate resonator; T(1)-T(2) relaxation correlation.