Electrochemical performance optimization of NMC811 through the structure design of its precursor

Abstract

This paper presents a study on the effect of the precursor structure on NMC811 electrochemical properties. The influence of different parameters, such as morphology and crystallinity of the precursor, Ni_0.8Mn_0.1Co_0.1(OH)₂, on the final electrochemical performance of NMC811 are analyzed. To ensure a correct and fast mixing of the precursor reactants and prepare the Ni_0.8Co_0.1Mn_0.1(OH)₂, a novel approach is used employing a micromixer, thus enabling the collection of the precipitated metal hydroxide within a few seconds after its precipitation. Then the precursor is calcinated together with a Li source to obtain the NMC811 cathode material. When analyzing the aging time of the precursor, between collection and calcination, it is observed that the primary particles of the precursor grow and become more crystalline, adopting a lamellar shape, while the secondary particles turn more compact, when increasing the aging time. The NMC materials synthesized from the aged precursors have smoother primary particles, exposing clearer crystalline planes. This change in morphology is also evidenced in the crystalline structure where an increase in the aging time produces better layered materials with a lower cation mixing index. The well-ordered structure impacts the electrochemical characteristics; indeed, the aged precursor produces NMC with higher specific capacity, better cyclability and lower capacity fade.