Li Plating on Carbon Electrode Surface Probed by Low-Field Dynamic Nuclear Polarization ^7Li NMR

Lithium deposition on graphite electrode not only reduces fast-charging capability of lithium ion batteries but also causes safety trouble. Here, a low-field ^7Li dynamic nuclear polarization (DNP) is used to probe Li plating on the surfaces of three types of carbon electrodes: hard carbon, soft carbon and graphite. Owing to the strong Fermi contact interaction between ^7Li and conduction electrons, the ^7Li nuclear-magnetic-resonance (NMR) signal of Li metal deposited on electrode surface could be selectively enhanced by DNP. It is suggested that low-field ^7Li DNP spectroscopy is a sensitive tool for investigating Li deposition on electrodes during charging/discharging processes.