High‐Rate Lithium–Selenium Batteries Boosted by a Multifunctional Janus Separator Over a Wide Temperature Range of −30 °C to 60 °C

Abstract Lithium–selenium batteries are characterized by high volumetric capacity comparable to Li–S batteries, while ≈10 25 times higher electrical conductivity of Se than S is favorable for high‐rate capability. However, they also suffer from the “shuttling effect” of lithium polyselenides (LPSes) and Li dendrite growth. Herein, a multifunctional Janus separator is designed by coating hierarchical nitrogen‐doped carbon nanocages (hNCNC) and AlN nanowires on two sides of commercial polypropylene (PP) separator to overcome these hindrances. At room temperature, the Li–Se batteries with the Janus separator exhibit an unprecedented high‐rate capability (331 mAh g −1 at 25 C) and retain a high capacity of 408 mAh g −1 at 3 C after 500 cycles. Moreover, the high retained capacities are achieved over a wide temperature range from −30 °C to 60 °C, showing the potential application under extreme environments. The excellent performances result from the “1+1>2” synergism of suppressed LPSes shuttling by chemisorption and electrocatalysis of hNCNC on the cathode side and suppressed Li‐dendrite growth by thermally conductive AlN‐network on the anode side, which can be well understood by the “Bucket Effect”. This Janus separator provides a general strategy to develop high‐performance lithium–chalcogen (Se, S, SeS 2 ) batteries.