The effect of hydrogen induced point defects on lithiation kinetics in manganese niobate anode

Abstract In this work, defective manganese niobate ( D -MNO) and its derivate ( D -MNO-600) have been applied as anode for lithium-ion batteries (LIBs). The Rietveld refinement indicates the presence of oxygen vacancy (Vo) and niobium deficiency in as-prepared two samples, which will perturb their crystalline lattices and lead the movement of the atoms to realize new equilibrium states. Unintentional hydrogen is introduced into D -MNO by two different interaction forms, one is bind with O atom to form OH/O− and another is trapped in Vo to form Ho. The interstitial hydrogen in crystal structure of D -MNO is the potential factor for its narrower bandgap energy (1.7 eV) and higher electronic conductivity (7.26 × 10−4 S cm−1) than D -MNO-600 (2.3 eV/2.39 × 10−4 S cm−1). Promisingly, a high reversible capacity of 225 mAh g−1 after 400 cycles is achieved in D -MNO under 1 A g−1, which is much better than D -MNO-600 (105 mAh g−1 at 1 A g−1). The further kinetics analysis shows the high pseudocapacitive contribution of 78% at 1 mV s−1 in D -MNO, suggesting its pseudocapacitive kinetics. Moreover, the observation of a slight left shifting in operando X-ray diffraction of D -MNO further demonstrates the absence of dramatical phase transfer during this pseudocapacitive electrochemical behavior. This finding of fast kinetics and superior stability in D -MNO will expand the horizon of fast-charging anode in LIBs.