Effect of non-stoichiometry on the charge storage capacity of NiO conversion anodes in Li-ion batteries

Abstract

Conversion anodes comprising non-stoichiometric black NiO suffer severe capacity fading in Li-ion batteries despite having a high Li+ ion diffusion coefficient. We attribute this capacity fading to (i) its small crystallite size (~ 8 nm) and (ii) high charge transfer resistance (Rct ~ 60–180 Ω cm2). Small crystallites enhance grain boundaries which promote Li+ ion diffusion without efficient material utilization. In contrast, the stoichiometric green NiO anodes deliver a stable capacity of 280 mAh g−1 over 50 charge-discharge cycles. The comparatively higher capacity of green NiO can be explained from its (i) large crystallite size (~ 104 nm) and (ii) negligible Rct values.