Unlock Restricted Capacity via OCe Hybridization for LiOxygen Batteries.

Abstract

The aprotic Li-O₂ battery (LOB) has the highest theoretical energy density of any rechargeable batteries. However, such system is largely restricted by the electrochemically formed lithium peroxide (Li₂ O₂ ) on the cathode surface, leading ultimately to low actual capacities and early cell death. In contrast to the surface-mediated growth of thin film with a thickness <50 nm, a non-crystalline Li₂ O₂ film with a thickness of >400 nm can be formed via an optimal OCe hybridized electronic structure. Specially, oxygen can react with dissolved cerium cations in the electrolyte via a cerium-oxygen reaction to form a high-energy faceted cerium oxide catalyst, which not only generates a great number of non-saturable active sites, but also erects electron transport bridges between the lattice O and adjacent Ce atoms. Such CeO orbital hybridization also forms a direct charge transfer channel from Ce-4f of CeO₂ to <math xmlns="http://www.w3.org/1998/Math/MathML"> <semantics> <mrow><msubsup><mi>O</mi> <mn>2</mn> <mrow><mn>2</mn> <mo>-</mo></mrow> </msubsup> </mrow> <annotation>${\rm{O}}_2^{2 - }$</annotation></semantics> </math> -π* of Li₂ O₂ , eventually leading to submicron-thick Li₂ O₂ shells via a subsequent lithium-oxygen reaction. Relying on the above merits, this work unlocks the rechargeable capacities of LOB from restricted 1000 to unprecedented 10 000 mAh g^-1 with good cyclabilities and reduced charge-discharge overpotentials.