A Hybrid LiCl/Li_xSn Conductive Interlayer to Unlock the Potential of Solid‐State Lithium Metal Batteries

Abstract Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) electrolyte has a great potential for application in solid‐state lithium metal batteries. However, due to the poor interfacial contact and thermodynamic instability between LATP and Li metal, a series of interfacial problems, such as high interfacial resistance, undesirable interfacial reaction and dendrite growth are deeply criticized. Herein, a hybrid LiCl/Li_xSn conductive interlayer is constructed through an in situ electrochemical reaction of SnCl₄ with Li metal to effectively improve the compatibility and stability of the Li/LATP interface. LiCl with both electronic insulation and high ionic conductivity can provide fast Li⁺ diffusion channel, block electron injection, avoid side reactions, and effectively inhibit dendrite growth. Li_xSn can reduce interfacial impedance, eliminate local electric field concentration, and significantly improve interfacial wettability. Under the protection of LiCl/Li_xSn hybrid interlayer, the initial resistance of the symmetric battery is reduced from 1066.3 to 133.6 Ω cm⁻², achieving a high critical current density of 1.4 mA cm⁻². At 0.1 mA cm⁻²/0.1 mAh cm⁻² and 0.2 mA cm⁻²/0.2 mAh cm⁻², the symmetric battery can cycle stably for more than 4000 h at 25 °C. Moreover, the full battery displays a high capacity retention ratio of 90.4% after 420 cycles at 0.5 C.