Multilayered, Bipolar, All‐Solid‐State Battery Enabled by a Perovskite‐Based Biphasic Solid Electrolyte

and excellent cycling stability over 100 cycles. Furthermore, a proof-of-concept bipolar ASSB comprising three unit cells connected in series is constructed by using the BSE membrane and Al/Cu-cladded bipolar plates. The bipolar ASSB shows high thermal stability and operates reversibly without any internal short circuit or current leakage during charge-discharge cycles; this demonstrates that BSEs provide a promising approach to the design and fabrication of bipolar ASSBs with improved safety and high energy density.