Enhanced Lithium-Ion Transport at Solid–Liquid Electrolyte Interface via Inorganic-Rich Layer for Quasi-Solid Electrolytes

The development of quasi-solid electrolytes composed of garnet-type Li7La3Zr2O12 (LLZO) with a liquid electrolyte represents a promising approach for safer lithium-ion batteries. However, a major challenge has been the inefficient transport of Li+ across the LLZO-liquid electrolyte interface due to the formation of a resistive interfacial layer. Herein, we systematically studied the relationship between interfacial Li+ transport and interfacial layer compositions controlled by heat treatment. We demonstrate that optimum heat treatment transforms the interfacial layer composition from organic-rich to inorganic-rich (including Li2CO3) without increasing the thickness, which significantly reduces the interfacial resistance and lowers the activation energy of Li+ transport. Furthermore, we achieved an enhanced limiting current density in a quasi-solid electrolyte using heat-treated LLZO. On this basis, an inorganic-rich interfacial layer, particularly with Li2CO3, is crucial for achieving efficient Li+ transport at solid–liquid electrolyte interfaces, offering an important guideline for developing advanced quasi-solid electrolytes.