Elevated-temperature behaviour of LiNi0.5Co0.2Mn0.3O2 cathode modified with rGO-SiO2 composite coating

An intense decrease in cycling performance and safety is a challenge for elevated temperature application of LiNi0.5Co0.2Mn0.3O2 (NCM) cathode material. In this paper, effect of two types of nano-coatings on improvement of elevated temperature performance of NCM cathode material has been investigated. One of the coatings contains SiO2 nanoparticles and the other one contains composite of reduced graphene oxide and SiO2 nanoparticles (rGO-SiO2). The coatings were fabricated by a facile wet chemical method. The SiO2 coated cathode material showed an excellent elevated temperature cycling stability, however, a decrease in discharge capacity and rate capability of this sample was observed. On the other hand, the composite coated cathode showed superior electrochemical properties as well as thermal stability. This sample showed a capacity retention of 80% compared to 46.1% for the pristine cathode after 100 cycles at 0.1C and 55 degrees C. The discharge capacity of the composite coated cathode at 2 and 5C was 146.9 and 126.7 mA h g(-1) which retains 79.2 and 69.3% of 185.5 mA h g(-1) at 0.1C and 55 degrees C. Based on the differential scanning calorimetry results, the surface modification with rGO-SiO2 shifted the exothermic peak of pristine cathode from 245.24 to 285.43 degrees C. Also, the composite coating reduced the transition metals dissolution of NCM cathode material at 55 degrees C. The enhanced performance at elevated temperature without scarifying other properties is related to presence of the composite coating on the surface of cathode particles: (i) SiO2 nanoparticles hinder the direct contact between the cathode and electrolyte and act as HF scavenger and (ii) reduced graphene oxide provides a conductive pathway on the cathode surface. Results of this work indicate that the rGO-SiO2 coated NCM cathode can be a suitable choice for LIBs industrial applications at elevated temperature. (C) 2020 Published by Elsevier B.V.