Effects of atmospheric Ti (III) reduction on Nb₂O ₅-doped Li₄Ti₅O₁₂ anode materials for lithium ion batteries

The effects of atmospheric annealing on electrochemical performance for Nb₂O₅-doped Li₄Ti₅O₁₂ anode materials have been investigated. The annealing of Nb₂O ₅-doped Li₄Ti₅O₁₂ in Ar-gas suppressed the capacity fade, under the condition of a high charge-discharge rate, by virtue of an enhanced exchange reaction at the electrode/electrolyte interface. Under Ar-gas, Nb₂O₅-doped Li₄Ti ₅O₁₂ was primarily reduced to increase the density of Ti³⁺ ions. This caused expansion of the Li₄Ti ₅O₁₂ lattice, but had little impact on Li-ion diffusion into the lattice. When concurrent doping and annealing induced such compositional and electrical modification of Li₄Ti₅O ₁₂, the polarization resistance of exchange reactions at the electrode/electrolyte interface decreased. Therefore, we have demonstrated that annealing in Ar-gas is capable of decreasing the resistance of exchange reactions at the electrode/electrolyte interface.