Observation of High‐Capacity Monoclinic B‐Nb2O5 with Ultrafast Lithium Storage

Abstract

AbstractApart from Li4Ti5O12, there are few anode substitutes that can be used in commercial high‐power lithium‐ion batteries. Orthorhombic T‐Nb2O5 has recently been proven to be another substitute anode. However, monoclinic B‐Nb2O5 of same chemistry is essentially inert for lithium storage, but the underlying reasons are unclear. In order to activate the “inert” B‐Nb2O5, herein, nanoporous pseudocrystals to achieve a larger specific capacity of 243 mAh g−1 than Li4Ti5O12 (theoretical capacity: 175 mAh g−1) are proposed. These pseudocrystals are rationally synthesized via a “shape‐keep” topological microcorrosion process from LiNbO3 precursor. Compared to pristine B‐Nb2O5, experimental investigations reveal that B‐Nb2O5−x delivers ≈3000 times higher electronic conductivity and tenfold enhanced Li+ diffusion coefficient. An ≈30% reduction of energy barrier for Li‐ion migration is also confirmed by the theoretical calculations. The nanoporous B‐Nb2O5−x delivers unique ion/electron transport channels to proliferate the reversible and deeper lithiation, which activate the “inert” B‐Nb2O5. The capacitive‐like behavior is observed to endow B‐Nb2O5−x ultrafast lithium storage ability, harvesting 136 mAh g−1 at 100 C and 72 mAh g−1 even at 250 C, superior to Li4Ti5O12. Pouch‐type full cells exhibit the energy density of ≈251 Wh kg−1 and ultrahigh power density up to ≈35 kW kg−1.