Multifunctional surface modification with Co-free spinel structure on Ni-rich cathode material for improved electrochemical performance

Abstract

In our previous work, a Li reactive-spinel coating using Co and Mn sources is suggested to solve microcracks and residual Li. However, the importance of reducing Co content is increasing due to the cost and environmental issues of Co as well as obstacles caused by patents. In this work, we focus on finding a coating material that can replace Co to overcome the shortcomings of Ni-rich cathode materials. The Ni/Hf coated sample with a multifunctional surface has a higher initial capacity compared to the pristine material. It is attributed to the decrease in residual Li, which hindered Li transportation. The rate capability (3 C/0.2 C) of the Ni/Hf = 2:1 sample is 90.8%. This is due to the unique 3D diffusion channels of the spinel structure. Thus, the Ni/Hf = 2:1 coated sample has a Li-ion diffusion coefficient higher than twice that of the pristine sample. Additionally, the coating layer suppress side reactions and large volume change, with higher reversibility of H2-H3. The charge-transfer resistance of the Ni/Hf = 2:1 coated sample is reduced by 48% compared to that of the pristine sample. Furthermore, it has an enhanced cycle retention of 89.6% after 50 cycles. The uniform Ni/Hf coating on the surface gave stability to the cathode powder, thereby improving performance compared to other coatings and pristine (c) 2022 Published by Elsevier B.V.