Recent Progress of Flexible Lithium–Air/O₂ Battery

Abstract

volume and improving its energy density. [39-47] Under the proposition of guaranteeing electrochemical performance, the components in the flexible metal-air battery, including active cathodes, metal anodes, separators, current collectors, and packaging materials, should be flexible to endure frequent mechanical strain. [48-54] Moreover, the safety of flexible battery is paramount during repeated deformation conditions. [55-60] Up to now, there are many flexible metal-air batteries have been proposed, such as flexible lithium (Li)-air battery, flexible Li-CO 2 battery, flexible zinc-air battery, flexible aluminum-air battery, silicon-oxygen battery, and so on. [61-71] Among various metalair batteries, Li-air batteries have raised much concern and got rapid development as a result of their theoretical energy density up to 5928 Wh kg −1 , eco-friendly, good reversibility, and high operating voltage of 2.96 V. [24,25,72-74] Here, we review the latest advances of flexible Li-air battery, focusing on the fabrication of flexible cathodes for improving the electrochemical performance, development of electrolyte for obtaining long durability, design of battery structure for achieving high flexibility. It should be noted that some reported studies on Li-air batteries were tested in the oxygen atmosphere rather than the ambient air, which is described as "Li-O 2 batteries." [27,75] 2. Flexible Cathodes The typical Li-air battery commonly made of Li metal anode, air cathode and aprotic electrolyte, which worked through the reaction of 2Li + O 2 → Li 2 O 2 (E OCV = 2.96 V). [76-80] As mentioned above, all components in flexible Li-air batteries should be flexible to accommodate stresses and strains in deformation. [10] However, the cathode and current collector are typically rigid carbon paper or porous metal, which hardly meet the needs of flexible Li-air battery, seriously restricting the development of the battery flexibility. [81-83] Moreover, the cathode should possess high catalytic activity to facilitate the OER and ORR reactions of Li-air battery, and porous structure to store the discharge products. [84-88] Therefore, it is urgently required to develop flexible and high-performance cathode materials with high mechanical stability for flexible Li-air batteries. Different from carbon paper with a rigid structure, carbon cloth is flexible that woven from multistrands of carbon fiber. Because of its mechanical flexibility and conductivity, carbon cloth was widely used as a flexible substrate material for the cathode in Li-air battery. [89-92] Liu et al. first proposed a flexible Li-O 2 battery with a flexible and recoverable cathode that constructed on the carbon cloth by depositing densely TiO 2 Along with the popularity of flexible electronic products, the requirements for flexible energy storage devices are also increasing, including high energy density, long-term stability, and high-grade safety. Among various flexible energy storage devices, flexible lithium-air batteries are expected to be one of the best candidate...

Recent progress and future perspectives of flexible metal‐air batteries

“…Compared with the brittleness and poor mechanical flexibility of inorganic solid electrolytes, polymer electrolytes have good flexibility, low interfacial impedance, and high ionic conductivity, which can be regarded as ideal flexible electrolytes, especially under repeated bending conditions 164 . Due to its good processing properties and mechanical strength, GPEs are considered as better candidates for aprotic flexible MABs.…”

“…Flexible carbon materials with the advantages of lighter weight, higher conductivity, larger surface area, and excellent flexibility have been regarded as favorable air cathodes in flexible LABs 164 . However, when CC, metal wire/mesh, or flexible wood is used as the substrate to load the cathode catalyst, the high weight of substrates will increase the overall weight and reduce the actual energy density of flexible LABs.…”

In Situ Anchoring Co–N–C Nanoparticles on Co4N Nanosheets toward Ultrastable Flexible Self‐Supported Bifunctional Oxygen Electrocatalyst Enables Recyclable Zn–Air Batteries Over 10 000 Cycles and Fast Charging

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the complex processes, low throughput, and high cost. [5][6][7] Among various novel flexible batteries, the aqueous rechargeable flexible Zinc-air battery (ZAB) with a semi-open structure is a promising candidate due to the high energy density of 1086 Wh kg −1 , high power density, low cost, environmentally friendliness, and high safety. [8][9][10][11][12] However, most of the reported ZABs are severely limited by the cycling performance and energy efficiency, resulting from the Zn dendrite formation and sluggish cathodic oxygen reduction/evolution reaction (ORR/OER).

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Critical review on development of magnesium alloy as anode inMg‐Airfuel cell and additives in electrolyte

“…Primary Mg‐air cells have been investigated since the late 50s and still undergoing progressive evolution starting with the rechargeable Mg2Ni‐air battery to secondary rechargeable MAFC using organic electrolytes 30,37‐39 . However, other metal‐air fuel cells especially Li‐air fuel cell are making huge progress and advancement in development of flexible energy storage system design following the trending revolution in flexible electronic 40‐43 where MAFC are still left behind.…”