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

Apart 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 approximate to 3000 times higher electronic conductivity and tenfold enhanced Li+ diffusion coefficient. An approximate to 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 approximate to 251 Wh kg(-1) and ultrahigh power density up to approximate to 35 kW kg(-1).