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Lithium–air battery (LAB) technology is currently being considered as a future technology for resolving energy and environmental issues. Here, we introduce recent advances and the remaining technical challenges in the development of LABs, particularly focusing on the cathodes based on a fundamental understanding of Li–O2electrochemistry.

Rechargeable metal-air batteries have attracted a great interest in recent years because of their high energy density. The critical challenges facing these technologies include the sluggish kinetics of the oxygen reduction-evolution reactions on a cathode (air electrode). Here, we report doped lanthanum nickelates (La2NiO4) with a layered perovskite structure that serve as efficient bifunctional electrocatalysts for oxygen reduction and evolution in an aqueous alkaline electrolyte. Rechargeable lithium-air and zinc-air batteries assembled with these catalysts exhibit remarkably reduced discharge-charge voltage gaps (improved round-trip efficiency) as well as high stability during cycling.

To realize all-solid-state lithium batteries, it is necessary to develop solid electrolytes with high ionic conductivity and stability. A total Li+ conductivity as high as 4.8 × 10−4 S cm−1 can be achieved for perovskite Li3xLa(2/3)−x□(1/3)−2xTiO3 at 25 °C via microstructural modifications.

There are increasing demands for large‐scale energy storage technologies for efficient utilization of clean and sustainable energy sources. Solid‐state lithium batteries (SSLBs) based on non‐ or less‐flammable solid electrolytes (SEs) are attracting great attention, owing to their enhanced safety in comparison to conventional Li‐ion batteries. Moreover, SSLBs can provide great benefits in terms of battery performance (power and energy densities) and cost when constructed using a bipolar design. In this review, we introduce the general aspects of the bipolar battery architecture and provide a brief overview of the essential components and technologies for bipolar SSLBs: Li+‐conducting SEs, composite electrodes, and bipolar plates. Furthermore, we review the recent progress in the design and construction of bipolar SSLBs with emphasis on the fabrication techniques of SEs and SSLBs and the engineering approaches to improve their electrochemical properties.

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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 Li La TiO perovskite and poly(ethylene oxide) (PEO) are reported. A flexible and freestanding BSE membrane exhibits high Li conductivity of about 1.2×10 S cm , 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 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.