Prolonging the cycling lifetime of lithium metal batteries with a monolithic and inorganic-rich solid electrolyte interphase

Abstract

An efficient solid electrolyte interphase (SEI) on the lithium (Li) metal anode is crucial for suppressing Li dendrites. Herein, a methoxide electrolyte additive, i.e., potassium methoxide, is revealed to induce preferential adsorption of anions on the Li metal surface by a combination of theoretical and experimental studies. Cryogenic transmission electron microscopy measurements and X-ray photoelectron spectroscopy depth profiles reveal that the as-formed inorganic-rich SEI possesses an amorphous and monolithic feature, which not only enables uniform diffusion of Li⁺ through the SEI but also reduces the diffusion barrier of Li⁺ along the Li/SEI interface. Consequently, Li dendrites can be efficiently suppressed and the cycling lifetime of Li|Li symmetric cells can be prolonged to 3500 h at 1 mA cm⁻²/1 mA h cm⁻². Besides, the LiFePO₄|Li full-cell batteries can be cycled stably over 400 cycles with an N/P ratio (i.e., the areal capacity ratio of the negative to positive electrodes) of ∼3 and a high LiFePO₄ mass loading of ∼20 mg cm⁻².