Self‐Suppression of Lithium Dendrite in All‐Solid‐State Lithium Metal Batteries with Poly(vinylidene difluoride)‐Based Solid Electrolytes

Polymer-based electrolytes have attracted ever-increasing attention for all-solid-state lithium (Li) metal batteries due to their ionic conductivity, flexibility, and easy assembling into batteries, and are expected to overcome safety issues by replacing flammable liquid electrolytes. However, it is still a critical challenge to effectively block Li dendrite growth and improve the long-term cycling stability of all-solid-state batteries with polymer electrolytes. Here, the interface between novel poly(vinylidene difluoride) (PVDF)-based solid electrolytes and the Li anode is explored via systematical experiments in combination with first-principles calculations, and it is found that an in situ formed nanoscale interface layer with a stable and uniform mosaic structure can suppress Li dendrite growth. Unlike the typical short-circuiting that often occurs in most studied poly(ethylene oxide) systems, this interface layer in the PVDF-based system causes an open-circuiting feature at high current density and thus avoids the risk of over-current. The effective self-suppression of the Li dendrite observed in the PVDF-LiN(SO₂ F)₂ (LiFSI) system enables over 2000 h cycling of repeated Li plating-stripping at 0.1 mA cm^-2 and excellent cycling performance in an all-solid-state LiCoO₂ ||Li cell with almost no capacity fade after 200 cycles at 0.15 mA cm^-2 at 25 °C. These findings will promote the development of safe all-solid-state Li metal batteries.