Highly conductive 3D structural carbon network-encapsulated Ni-rich LiNi0.8Co0.1Mn0.1O2 as depolarized and passivated cathode for lithium-ion batteries

Abstract

Various encapsulation methods have been proposed thus far to improve the electrochemical performance of Ni-rich LiNixCoyMnzO2 (NCM, x + y + z = 1). Among them, carbon encapsulation is superior to other coatings for enhancing the depolarization of Ni-rich NCM. However, the sensitivity to moisture and reduction conditions of the Ni-rich NCM restricts the application of carbon encapsulation processes under high temperature or strong reduction environments, which can decompose carbon structures or degrade the Ni-rich NCM. To overcome this problem, in this study, a highly conductive and ethanol-dispersive 3D carbon network is assembled using 6-amino-4-hydroxy-2-naphthalenesulfonic acid (AHNS)-functionalized rGO and carbon nanotubes (CNTs) and uniformly coated on LiNi0.8Co0.1Mn0.1O2 (NCM811). The conductive 3D carbon network layer on the NCM811 surface facilitates the transport of electrons and ions, enhancing the depolarization of the NCM811, which enables it to achieve stable electrochemical reactions at high rates. In addition, the 3D carbon network layer prevents the electrical separation caused by micro-cracks in NCM811, irreversible phase transitions, and side reactions with electrolytes that can occur during the charging/discharging processes. Consequently, the 3D carbon network layer-encapsulated NCM811 shows a high discharge capacity of 125 mAh g−1 at 10C/10C charge/discharge rates and excellent capacity retention of 88% after 100 cycles at 1C/1C. Compared with bare NCM811, the rate capability and cycle stability of the 3D carbon network layer-encapsulated NCM811 are improved by 423% and 35%, respectively.