Li 2 Se: A High Ionic Conductivity Interface to Inhibit the Growth of Lithium Dendrites in Garnet Solid Electrolytes.

All-solid-state Li metal batteries (ASSLBs) are currently regarded as one of the most promising next-generation energy storage technologies because of their great potential in realizing both high energy density and safety. However, the development of high performance ASSLBs is still restricted by the large interfacial resistance and Li dendrite propagation within solid electrolytes. Herein, a simple and efficient interfacial modification strategy is proposed to improve the interfacial contact between Li and Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) by introducing a uniform and thin Li 2 Se buffer layer. The Li 2 Se buffer layer formed by an in situ conversion reaction can not only enhance the wettability of lithium metal toward LLZTO electrolyte but also facilitate uniform lithium plating/stripping. As a result, the interfacial resistance of Li/LLZTO decreased from 270.5 to 5.1 Ω cm 2 , and the lithium symmetric cell can cycle stably for 350 h at a current density of 0.5 mA cm -2 . Meanwhile, the Li|LLZTO-Li 2 Se|LiNi 0.8 Co 0.1 Mn 0.1 O 2 full cells exhibit a high initial capacity of 162.3 mAh g -1 and good cycling stability with a capacity retention of 84.3% after 100 cycles at 0.2 C. These results prove the effectiveness of this modification method and provide new design strategies for the development of high performance ASSLBs.