Three-dimensional alloy interface between Li_6.4La₃Zr_1.4Ta_0.6O₁₂ and Li metal to achieve excellent cycling stability of all-solid-state battery

The interfacial issues between garnet electrolyte and Li metal hinder the application of garnet electrolyte in solid-state Li metal batteries. Herein, a three-dimensional (3D) porous Zn layer (PZL) is magnetron sputtered on the surface of Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) to construct a 3D Li–Zn alloy layer at the LLZTO/Li interface by melting Li metal into PZL. The 3D Li–Zn alloy effectively reduces the LLZTO/Li interfacial impedance from 319.8 Ω cm² to an extremely low value of 1.9 Ω cm². Meanwhile, the 3D alloy skeleton can enhance the transport kinetics and promote uniform distribution of Li ion at interface to inhibit the growth of Li dendrites. More importantly, the volume expansion of interface between LLZO and Li metal anode is effectively suppressed due to the host role of 3D Li–Zn alloy interface. The Li/LLZTO@PZL/Li symmetrical battery achieves a high critical current density of 2 mA cm⁻² for one cycle. The all-solid-state LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523)/LLZTO@PZL/Li battery with a high cathode loading of 4.9 mg cm⁻² delivers a high specific capacity of 143.8 mAh g⁻¹ after 170 cycles. The 3D alloy interface is significant for enhancing the interfacial stability of high capacity all-solid-state lithium metal batteries.