Growth mechanisms for spherical Ni0.815Co0.15Al0.035(OH)2 precursors prepared via the ammonia complexation precipitation method

The microstructures of precursors strongly affect the electrochemical performance of Ni-rich layer-structured cathode materials. In this study, the growth behaviour of Ni0.815Co0.15Al0.035(OH)2 (NCA) prepared via the ammonia complexation precipitation method in a 50-L-volume continuously stirred tank reactor (CSTR) is studied in detail. The growth of Ni(OH)2-based hydroxide can be divided into a nucleation process, an agglomeration growth process, a process in which multiple growth mechanisms coexist, and an interface growth process over time, while the inner structure of the CSTR can be divided into a nucleation zone, a complex dissolution zone, a growth zone, and a maturation zone. The concentration of ammonium ions affects the growth habit of the primary crystal significantly due to its specific adsorption on the electronegative crystal plane. When the ammonia concentration is <1.5 mol L−1 at 60 °C at pH = 11.5, the precursors grow preferentially along the (1 0 1) crystal plane, whereas they grow preferentially along the (0 0 1) crystal plane when the concentration is >2.0 mol L−1. The LiNi0.815Co0.15Al0.035O2 materials inherit the grain structure of the precursor. Materials prepared from precursors with (1 0 1) preferential primary particles show a higher specific capacity and better rate performance than those that were prepared from (0 0 1) preferential primary particles, but the latter realize a better cycling performance than the former.