Dry carbon nanotube wrapping of Ni-rich layered oxide cathodes for lithium-ion batteries

Abstract

The highly conductive carbon nanotubes (CNT) coating for the Ni-rich layered oxide cathode materials is proposed for use in lithium-ion batteries (LIBs). Unlike the conventional carbon coating method, a novel dry CNT coating technique onto the active material particle without heating is developed to avoid carbo-thermal reduction causing oxide deterioration by CO₂ generation at high coating temperature. The shear stress of dry coating delivers sculpted short lengths of coating CNTs, which ensure high coating coverage as well as optimal electron transportation and distributions. Dry-tailored CNT coatings have multi-functions of mitigating surface degradation and improving electrical conductivity. With a small content of inactive conducting agents in the electrode, CNT-coated cathodes enhance cyclability and rate capability. Ni-rich LiNi_0.89Co_0.06Mn_0.05O₂ (NCM) powder with a small amount of CNT coating significantly improves electrochemical performance than that of conventional electrodes using the same amount of conductive additives such as super-C and CNT. The CNT coating on NCM also enables graphite (Gr||NCM) full cells to have a high specific energy density, which is improved from 284.7 to 308.7 Wh kg⁻¹, simultaneously achieving an excellent energy retention of 75.0 % after 250 cycles. This research offers an efficient dry coating technique for achieving high energy density in LIBs.