Observation of High-Capacity Monoclinic B-Nb 2 O 5 with Ultrafast Lithium Storage.

Apart from Li 4 Ti 5 O 12 , there are few anode substitutes that can be used in commercial high-power lithium-ion batteries. Orthorhombic T-Nb 2 O 5 has recently been proven to be another substitute anode. However, monoclinic B-Nb 2 O 5 of same chemistry is essentially inert for lithium storage, but the underlying reasons are unclear. In order to activate the "inert" B-Nb 2 O 5 , herein, nanoporous pseudocrystals to achieve a larger specific capacity of 243 mAh g -1 than Li 4 Ti 5 O 12 (theoretical capacity: 175 mAh g -1 ) are proposed. These pseudocrystals are rationally synthesized via a "shape-keep" topological microcorrosion process from LiNbO 3 precursor. Compared to pristine B-Nb 2 O 5 , experimental investigations reveal that B-Nb 2 O 5- 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-Nb 2 O 5- x delivers unique ion/electron transport channels to proliferate the reversible and deeper lithiation, which activate the "inert" B-Nb 2 O 5 . The capacitive-like behavior is observed to endow B-Nb 2 O 5- x ultrafast lithium storage ability, harvesting 136 mAh g -1 at 100 C and 72 mAh g -1 even at 250 C, superior to Li 4 Ti 5 O 12 . Pouch-type full cells exhibit the energy density of ≈251 Wh kg -1 and ultrahigh power density up to ≈35 kW kg -1 .