Negating Li+ transfer barrier at solid-liquid electrolyte interface in hybrid batteries

Solid-state batteries are highly desirable for replacing traditional Li-ion batteries to offer higher energy density and safety. However, the usage of ceramic-based solid-state electrolytes (CSSEs) leads to large interfacial resistances owing to the undesirable contact with electrodes. A small amount of organic liquid electrolyte (LE) is usually added to solve this issue. Unfortunately, a spontaneous Li+/H+ exchange reaction occurs due to the trace of proton impurity in LE accompanied by the chemical adsorption of organic decomposition, giving rise to a gradually thickened LE-CSSE interphase. Here, we demonstrate that the LE-CSSE interface can be stabilized by nanometer-scale self-assembled monolayers (SAMs) with acidic anchoring groups in which either the in situ Li+/H+ exchange or the strong interaction between CSSE and decompositions can be efficiently weakened. With the assistance of the consumption of surface Li+ concentration and the compact SAM passivating layer, unprecedented impedance approaching to zero is achieved for the active LE-CSSE interface.