Organophosphorus decorated lithium borate and phosphate salts with extended π-conjugated backbone

Several new bifunctional salts, Li[B(DPN)₂], Li[B(DPN)(ox)] and Li[P(DPN)₃], have been prepared from the phosphorus(v)-containing chelating ligand 2,3-dihydroxynaphthalene-1,4-(tetraethyl)bis(phosphonate) (H₂-DPN). The new lithium salts were characterized by a variety of spectroscopic techniques. Both H₂-DPN and Li[B(DPN)₂] have been structurally characterized by X-ray crystallographic methods. These salts are related to materials being examined for use in electrolyte solutions for lithium-ion battery (LIB) applications.

Operando Tracking of Solution-Phase Concentration Profiles in Li-Ion Battery Positive Electrodes Using X-ray Fluorescence

The trade-off between energy density and power capabilities is a challenge for Li-ion battery design as it highly depends on the complex porous structures that holds the liquid electrolyte. Specifically, mass-transport limitations lead to large concentration gradients in the solution-phase and subsequently to crippling overpotentials. The direct study of these solution-phase concentration profiles in Li-ion battery positive electrodes has been elusive, in part because they are shielded by an opaque and paramagnetic matrix. Herein we present a new methodology employing synchrotron hard X-ray fluorescence to observe the concentration gradient formation within Li-ion battery electrodes in operando. This methodology is substantiated with data collected on a model LiFePO₄/Li cell using a 1 M LiAsF₆ in 1:1 ethylene carbonate/dimethyl carbonate (EC/DMC) electrolyte under galvanostatic and intermittent charge profiles. As such, the technique holds great promise for optimization of new composite electrodes and for numerical model validation.