A magnetic-assisted construction of functional gradient interlayer for dendrite-free solid-state lithium batteries

Garnet-based solid-state Li batteries are considered as important candidates of the next generation batteries due to their potentially high energy density and reliable safety, however the Li dendrite issue is a serious impediment to their further development. Herein, a functional gradient interlayer (FGIL) is introduced at the interface between the garnet and Li anode, which is formed by the in-situ reaction of molten Li with FeF₃ assisted by a magnetic force. The FGIL not only reduces the interfacial impedance, evens out the local current distribution, and prevents the growth of Li dendrites on the electrode surface, but also blocks electron transport and prevents the formation of "Li filaments" inside the electrolyte. Consequently, the Li|LLZTO-FGIL|Li cells have a critical current density of up to 2.3 mA cm⁻² and exhibit stable cycling for more than 3400 h at 0.3 mA cm⁻².