A self-regulated gradient interphase for dendrite-free solid-state Li batteries

Solid-state Li metal batteries (SSLMBs) have emerged as an important energy storage technology that offers the possibility of both high energy density and safety by combining a Li metal anode (LMA), a high-capacity cathode and a nonflammable solid-state electrolyte (SSE). However, the major challenges of poor LMA/SSE interface wetting and the easy growth of Li dendrites in SSEs remain unsolved. Here, we have addressed these challenges by using a functional gradient Li anode (FGLA), which is formed through a self-regulated reaction between molten Li and AlF3. A composition gradient of Li-LiAl-LiF is spontaneously formed from the reaction of molten Li with AlF3 due to the large difference in interfacial energy between Li/LiAl and Li/LiF, where the LiAl reduces the interface resistance and LiF suppresses Li dendrites. The FGLA not only dramatically reduces the resistance at the FGLA/Li6.5La3Zr1.5Ta0.5O12 (LLZTO) garnet SSE interface to similar to 1 omega cm(-2), but also largely increases the critical current density (CCD) to over 3.0 mA cm(-2) at room temperature. Moreover, the full cells paired with LiNi0.5Co0.2Mn0.3O2, sulfur and thick LiFePO4 cathodes (similar to 2.8 mA h cm(-2)) also show excellent cycling performances. The FGLA design provides a great opportunity for safe and high-energy SSLMBs.

Automated summary

This study addresses the major challenges in solid-state Li metal batteries (SSLMBs) by using a functional gradient Li anode (FGLA), which reduces the interface resistance and suppresses Li dendrite growth. The FGLA not only dramatically reduces the resistance at the interface, but also increases the critical current density, showing excellent cycling performances with different cathode materials.