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

Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 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 x Sn conductive interlayer is constructed through an in situ electrochemical reaction of SnCl 4 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 x Sn can reduce interfacial impedance, eliminate local electric field concentration, and significantly improve interfacial wettability. Under the protection of LiCl/Li x Sn 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.