Spontaneous In Situ Formation of Lithium Metal Nitride in the Interface of Garnet-Type Solid-State Electrolyte by Tuning of Molten Lithium

All-solid-state lithium-ion batteries (ASSLIBs) have attracted much attention owing to their high energy density and safety and are known as the most promising next-generation LIBs. The biggest advantage of ASSLIBs is that it can use lithium metal as the anode without any safety concerns. This study used a high-conductivity garnet-type solid electrolyte (Li_6.75La₃Zr_1.75Ta_0.25O₁₂, LLZTO) and Li-Ga-N composite anode synthesized by mixing melted Li with GaN. The interfacial resistance was reduced from 589 to 21 Ω cm², the symmetry cell was stably cycled for 1000 h at a current density of 0.1 mA cm^-2 at room temperature, and the voltage range only changed from ±30 to ±40 mV. The full cell of Li-Ga-N|LLZTO|LFP exhibited a high first-cycle discharge capacity of 152.2 mAh g^-1 and Coulombic efficiency of 96.5% and still maintained a discharge capacity retention of 91.2% after 100 cycles. This study also demonstrated that Li-Ga-N had been shown as two layers. Li₃N shows more inclined to be closer to the LLZTO side. This method can help researchers understand what interface improvements can occur to enhance the performance of all-solid-state batteries in the future.