Abstract
The major challenge facing lithium–oxygen batteries is the insulating and bulk lithium peroxide discharge product, which causes sluggish decomposition and increasing overpotential during recharge. Here, we demonstrate an improved round-trip efficiency of ~80% by means of a mesoporous carbon electrode, which directs the growth of one-dimensional and amorphous lithium peroxide. Morphologically, the one-dimensional nanostructures with small volume and high surface show improved charge transport and promote delithiation (lithium ion dissolution) during recharge and thus plays a critical role in the facile decomposition of lithium peroxide. Thermodynamically, density functional calculations reveal that disordered geometric arrangements of the surface atoms in the amorphous structure lead to weaker binding of the key reaction intermediate lithium superoxide, yielding smaller oxygen reduction and evolution overpotentials compared to the crystalline surface. This study suggests a strategy to enhance the decomposition rate of lithium peroxide by exploiting the size and shape of one-dimensional nanostructured lithium peroxide.
Highlights
The major challenge facing lithium–oxygen batteries is the insulating and bulk lithium peroxide discharge product, which causes sluggish decomposition and increasing overpotential during recharge
As the mesoporous carbon electrode in Li–O2 cells, CMK-3 was employed without the use of any additive carbon
At the initial stage of DC with CMK-3, we found that the overpotential of oxygen reduction reaction (ORR), which leads to the formation of amorphous
Summary
The major challenge facing lithium–oxygen batteries is the insulating and bulk lithium peroxide discharge product, which causes sluggish decomposition and increasing overpotential during recharge. Current battery technology supplies far lower gravimetric and volumetric energy densities compared to fossil fuels, which has propelled the development of advanced batteries[3] In this regard, the rechargeable lithium–oxygen (Li–O2) battery is one of the most suitable concepts with the essential precondition of high theoretical energy density (~3 kWh kg−1). Li2O2 decomposition at little expense of overpotential is highly necessary, which has led to the concerted effort in developing catalysts[10,11] including heterogeneous[12,13,14] and soluble molecular catalysts[15,16,17] These catalysts have shown suppressed RC potentials, but they have caused unintended problems, such as the degradation of electrolyte solution[18] and shuttling of soluble molecules that passivate the negative Li electrode[19,20]. Li2O2 facilely decomposes from the surface, corresponding to the Li2O2/ electrolyte solution interface at potentials below 3.5 V21,23,24
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