Identifying the lithium bond and lithium ionic bond in electrolytes

Lithium (Li) chemistry has been a significant branch of modern chemistry due to its wide and critical applications, such as Li batteries. Similar to the hydrogen (H) bond, the Li bond is the central topic of Li chemistry, but its nature is far from clear. Herein, the fundamental chemistry of the Li bond is systematically investigated, taking Li battery electrolytes as an example. Specifically, the Li bond and Li ionic bond can be differentiated according to nuclear magnetic resonance spectroscopy as ⁷Li chemical shifts exhibit a downfield and upfield shift, respectively. The downfield shift indicates an electron localization effect of the Li bond beyond electrostatic interactions, which mainly dominate the ionic bond. Bond and electronic structure analyses further verify the difference between these two bonds. This work establishes principles to identify the Li bond and Li ionic bond, which contribute to Li chemistry and related applications, such as Li batteries.