A Double-Buffering Strategy to Boost the Lithium Storage of Botryoid MnOx /C Anodes.

Transition metal oxides (TMOs) are regarded as promising candidates for anodes of lithium ion batteries, but their applications have been severely hindered by poor material conductivity and lithiated volume expansion. As a potential solution, herein is presented a facile approach, by electrospinning a manganese-based metal organic framework (Mn-MOF), to fabricate yolk-shell MnOx nanostructures within carbon nanofibers in a botryoid morphology. While the yolk-shell structure accomodates the lithiated volume expansion of MnOx , the fiber confinement ensures the structural integrity during charge/discharge, achieving a so-called double-buffering for cyclic volume fluctuation. The formation mechanism of the yolk-shell structure is well elucidated through comprehensive instrumental characterizations and cogitative control experiments, following a combined Oswald ripening and Kirkendall process. Outstanding electrochemical performances are demonstrated with prolonged stability over 1000 cycles, boosted by the double-buffering design, as well as the "breathing" effect of lithiation/delithiation witnessed by ex situ imaging. Both the fabrication methodology and electrochemical understandings gained here for nanostructured MnOx can also be extended to other TMOs toward their ultimate implementation in high-performance lithium ion batteries (LIBs).