Structural and Chemical Evolution of Amorphous Nickel Iron Complex Hydroxide upon Lithiation/Delithiation

Development of novel electrode materials is essential to achieve high-performance lithium ion batteries. Here, we demonstrate that amorphous nickel iron complex hydroxides (Ni-Fe-OH) synthesized by a laser-chemical method can be used as a potential conversion anode material for lithium storage. Complementary characterizations, including ensemble-averaged X-ray absorption spectroscopy, spatially resolved electron energy-loss spectroscopy, and energy dispersive X-ray spectroscopy in a scanning transmission electron microscope, were performed to reveal the chemical and structural evolutions of the active hydroxide particles undergoing electrochemical cycling. The solid-electrolyte interphase (SEI) layer with a primary component of lithium fluoride (LiF) was found and remained robust on the particle surface during the charge/discharge processes, which suggests that the LiF-containing SEI layer plays a critical role in maintaining the stable capacity retention and good reversibility of the Ni-Fe-OH anode.