Dilithium phthalocyanine as electrolyte additive for the regulation of ion solvation and transport towards dendrite-free Li metal anodes

Abstract

The application of Li metal anodes in high energy–density batteries is hindered by the uncontrolled dendrite growth and rapid capacity fading. Herein, we demonstrate that dilithium phthalocyanine (Li2Pc) is highly effective for the regulation of ion solvation and transport towards dendrite-free Li metal anodes. The strong interactions of Li2Pc with the solvents generate an apparent solvation sheath surrounding the large phthalocyanine ligand, where the dipole–dipole interactions of the solvents are weakened. This promotes the anion solvation in the outer solvation sheath, which suppresses the mobility of the anions for apparently increased Li+ transference number and facilitates the dissociation of the solute for a higher ionic conductivity. The resulting uniform Li+ flux alleviates the space charge to impede the growth of dendrites. Stable Li plating/stripping of 800 h (1 mA cm−2, 1 mAh cm−2) and dendrite-free Li deposition up to 10 mA cm−2, 10 mAh cm−2 are achieved in Li/Li cells and the Li/Cu cells exhibit a high average CE of 98.3% over 150 cycles at 1 mA cm−2, 1 mAh cm−2. Stable cycling of Li-S full cells at the condition of N:P = 2:1 are also demonstrated with high average CEs of 98.29%.