Orderly Arranged Dipoles Regulate Anion-Derived Solid-Electrolyte Interphase for Stable Lithium Metal Chemistry

Abstract

Lithium (Li) metal batteries are considered the most promising high-energy-density electrochemical energy storage devices of the next generation. However, the unstable solid-electrolyte interphase (SEI) derived from electrolytes usually leads to high impedance, Li dendrites growth, and poor cyclability. Herein, the ferroelectric BaTiO₃ with orderly arranged dipoles (BTOV) is integrated into the polypropylene separator as a functional layer. Detailed characterizations and theoretical calculations indicate that surface oxygen vacancies drive the phase transition of BaTiO₃ materials and promote the ordered arrangement of dipoles. The strong dipole moments in BTOV can adsorb TFSI^- and NO₃ ^- anions selectively and promote their preferential reduction to form a SEI film enriched with inorganic LiF and LiN_xO_y species, thus facilitating the rapid transfer of Li⁺ and restraining the growth of Li dendrites. As a result, the Li-Li cell with the BTOV functional layer exhibits enhanced Li plating/stripping cycling with an ultra-long life of over 7000 h at 0.5 mA cm^-2/1.0 mAh cm^-2. The LiFePO₄ || Li (50 µm) full cells display excellent cycling performance exceeding 1760 cycles and superior rate performance. This work provides a new perspective for regulating SEI chemistry by introducing ordered dipoles to control the distribution and reaction of anions.

Keywords: Li metal batteries; orderly arranged dipoles; solid–electrolyte interphase; surface oxygen vacancies (OVs); the reduction of anions.