Towards an efficient anode material for Li-ion batteries: Understanding the conversion mechanism of nickel hydroxy chloride with Li-ions

Heterostructured nanocomposites comprising transition metal compounds (TMCs) with different bandgaps are attractive due to their excellent electrochemical performances. Candidates that combine various cations and anions are actively researched. Herein, it is demonstrated for the first time that nickel hydroxy chloride, once transformed into a heterostructured nanocomposite during the initial cycle, can be used as a new anode material for lithium-ion storage. In particular, the reaction mechanism for lithium-ion storage with a metal hydroxy chloride as the anode is demonstrated through various analyses for the first time. The model compound, nickel hydroxy chloride (Ni(OH)Cl), prepared by a one-pot hydrothermal method, is used to investigate the detailed conversion mechanism in Li-ion storage. Through systemically analyzed results, it is demonstrated that Ni(OH)Cl is transformed into Ni(OH)₂ and NiCl₂ after one cycle and that the layered Ni(OH)₂/NiCl₂ nanocomposite heterointerface reacts with Li ions from the second cycle onward. Flower-like Ni(OH)Cl microspheres display extremely high and stable cycling performance (1236 mA h g^-1 for the 150th cycle at a current density of 0.2 A g^-1) and outstanding rate capability (232 mA h g^-1) at an extremely high current density of 30 A g^-1,.