In Situ and Low-Cost Improvement of the Lithium Anode Interface in Garnet-Type Solid-State Electrolytes

In recent years, the development of electric vehicles and environmental concerns have made necessary improvements in the energy density and safety of lithium-ion batteries. Therefore, the development of all-solid-state lithium-ion batteries (ASSLIBs) has become imperative. One advantage of ASSLIBs is their potential for downsizing with the use of lithium metal as the anode. However, in this study, a garnet-type solid electrolyte (Li_6.75La₃Zr_1.75Ta_0.25O₁₂) was used, which has low reactivity with lithium metal. Thus, interface modification using CaCl₂ was employed to form a Li-Ca-Cl composite anode. The interfacial resistance was remarkably reduced to 7 Ω cm², and the symmetric cell exhibited stable cycling for 1200 h at room temperature and a current density of 0.1 mA cm^-2. The voltage ranged from ±15 to ±16 mV. The full cell demonstrated a high initial discharge capacity of 149.2 mA h g^-1 and a Coulombic efficiency of 98.0% while maintaining a discharge capacity retention of 91.3% after 100 cycles. These findings lay a solid foundation for future commercial applications as interface modification was achieved through a simple spin-coating process using low-cost CaCl₂ (0.7 USD g^-1).