In-situ constructed lithium-salt lithiophilic layer inducing bi-functional interphase for stable LLZO/Li interface

Abstract

Solid-state lithium (Li) metal battery is promising for next-generation battery systems due to its high safety and expected high energy density. Li7La3Zr2O12 (LLZO) with superior ionic conductivity and excellent stability with Li stands out among numerous solid electrolytes, yet the poor interfacial contact and the growth of dendrites hinder its application. Herein, a lithium-salt lithiophilic layer with nano-porous structure is constructed on the garnet surface by using H3BO3 aqueous solution and HF vapor. The violent reaction of lithium-salt layer with Li coupled with capillary force from nano-porous layer give rise to superior lithiophilicity, which greatly improves the wettability of LLZO with molten Li, thereby reducing the interfacial impedance to ∼9 Ω cm2. The interfacial reaction induces bi-functional interphase with electronically insulation and high surface energy, which can block the electron transport at the interface and guide the horizontal deposition of lithium, thus effectively suppressing the Li dendrites. With above effects, a stable LLZO/Li interface is obtained with an improved critical current density (CCD) of ∼2 mA cm−2 and excellent cycling stability for 1200 h at 0.5 mA cm−2 at 25 ℃. And the solid batteries with LiFePO4 or LiNi0.5Co0.2Mn0.3O2 cathode display excellent long-term cycling performance and can work normally at 1.2 mA cm−2 at 25 ℃.