In situ X-ray diffraction investigation of zinc based electrode in Ni-Zn secondary batteries

In situ/in operando X-ray diffraction coupled with electrochemical cycling of ZnO based electrodes in KOH electrolyte has been used as a powerful tool in order to investigate the influence of additives. The technique has been performed in order to highlight the role of bismuth based conductive additives on the cycling ability of the electrode. It enables to clearly evidence the conversion of zinc oxide to zinc metal. During the first charge, it also helps to visualize the conversion of Bi2O3 additive into metallic bismuth prior to ZnO reduction which leads to the formation of an electronic pathway at the nanometer scale complementary from the current collector and the TiN percolation conductive network. Additionally, each Bi2O3 grain seems to be converted in a single bismuth grain which is not agglomerated with other bismuth particles even after 50 cycles. This behaviour leads to a steady capacity of the zinc based electrode compared to the same electrode without Bi2O3 additive. Subsequently, in situ XRD investigation of Zn based negative electrode in nickel-zinc batteries can be a powerful tool to design new composite electrode with long term cycling efficiency.