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

The use of solid electrolytes provides a technical solution to address the safety issues of lithium‐ion batteries and enables a bipolar design of high‐voltage and high‐energy battery modules. The bipolar design avoids unnecessary components and parts for packaging and electrical connection; therefore, it facilitates an increase in the volumetric energy density of the battery, while enabling easy build‐up of total output voltage. Herein, the design and construction of a multilayered, bipolar‐type, all‐solid‐state battery (ASSB) from a biphasic solid electrolyte (BSE) based on inorganic Li0.29La0.57TiO3 perovskite and poly(ethylene oxide) (PEO) are reported. A flexible and freestanding BSE membrane exhibits high Li+ conductivity of about 1.2×10−4 S cm−1, and shows enhanced electrochemical/thermal stability, in comparison to a PEO‐only solid electrolyte. A single‐layered ASSB assembled with a BSE shows promising electrochemical performance, as evidenced by a high reversible capacity of about 123 mA h g−1 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.