Two Better Than One: Enhanced Photo‐Assisted Li‐O₂ Batteries with Bimetallic Fe‐UiO‐66 Metal‐Organic Framework Photocathodes

Abstract

Li‐O2 batteries, known for their impressive theoretical specific energy, face significant practical challenges, including slow kinetics, voltage hysteresis, and reduced cycle life. In this study, a novel approach is introduced utilizing a bimetallic metal‐organic framework known as Fe‐UiO‐66 as a multifunctional photocatalyst to enhance the oxygen‐related reactions in photo‐assisted Li‐O2 batteries. In contrast to UiO‐66, Fe‐UiO‐66 exhibits an extended response to visible light, as confirmed through UV–vis and photoluminescence spectra. Electron paramagnetic resonance analysis provides further validation of the pivotal role played by O2− radicals in the electrochemical processes. Additionally, computations are employed to elucidate the distinct function of Fe centers and the underlying reaction mechanisms. Li‐O2 batteries with Fe‐UiO‐66 cathodes have a reduced charge/discharge voltage difference of 0.14 V under illumination and operate stably for 500 cycles. This work encourages MOF‐based photocathode development for Li‐O2 batteries.

Exciton Dissociation into Charge Carriers in Porphyrinic Metal‐Organic Frameworks for Light‐Assisted Li‐O2 Batteries

“…The accumulated LiO 2 then undergoes further reduction or disproportionation to form Li 2 O 2 film with amorphous features on the surface of FeNi-TCPP electrode. [26] During the charging process, the photogenerated holes in FeNi-TCPP actively participate in the oxidation of…”

From Li–O2 to Li–Air Batteries: Challenges and Progress on Oxygen-Permeable Membranes

“…However, the energy density of existing lithium-ion batteries is approaching its limit, and the exceedingly high cost of application in electric vehicles makes achieving a range of 500 miles per charge highly improbable. 5,6 As one of the most promising candidates for power sources, rechargeable Li−air batteries (LABs) possess a theoretical energy density of up to 3500 Wh kg −1 , which is 5−10 times higher than that of conventional lithium-ion batteries, and exhibit the highest theoretical specific energy density of 11 680 Wh kg −1 among known metal-based electrochemical batteries. 7 The high energy density can be attributed to two main factors: (i) The negative electrode material (metallic lithium) of LABs is the lightest metal, with a high specific capacity of 3860 mAh g −1 and the lowest electrochemical potential [−3.04 V versus standard hydrogen electrode (SHE)]; (ii) Unlike most energy storage devices, the active material (oxygen) of LABs is not stored internally but continuously sourced from the surrounding air, without adding to the battery's weight or volume.…”

“…The transition from fossil fuel vehicles to hybrid and electric cars has become inevitable. However, the energy density of existing lithium-ion batteries is approaching its limit, and the exceedingly high cost of application in electric vehicles makes achieving a range of 500 miles per charge highly improbable. , …”