Reticular Elastic Solid Electrolyte Interface Enabled by an Industrial Dye for Ultrastable Potassium‐Ion Batteries

The solid electrolyte interface (SEI) is vital to the stability of alkali metal‐ion battery anodes. However, conventional SEIs that lack elasticity will be damaged during the anode's repeated volume expansion, such as in potassium‐ion battery anodes, ultimately resulting in cell failure. Herein, a low‐content additive (pigment green 7, 0.07 wt%) in a conventional carbonate electrolyte to create a reticular elastic SEI with excellent uniformity and good chemical stability is employed. As a result, long‐lasting K||K symmetric cell (over 1400 h), enhanced graphite anode (500 cycles with 97.9% capacity retention), and stabilized perylene‐3,4:9,10‐tetracarboxydiimide cathode (1200 cycles with 82.8% capacity retention) are achieved. Furthermore, the matched graphite||perylene‐3,4:9,10‐tetracarboxydiimide full cell operates stably for more than 200 cycles. This work provides a novel avenue into the rational design of elastic SEIs for advanced anodes.