Coating Ni-rich cathode with an amorphous carbon for improving the stability and electrochemical performance

Layer-structured Ni-rich cathodes are promising candidates for high-energy-density lithium-ion batteries (LIBs). However, Ni-rich cathodes still suffer from fast capacity fading and voltage dropping issues due to surface phase reconstruction, oxygen release, and intergranular/intragranular cracking problems. To tackle these issues, herein, we coating Ni-rich cathodes with an amorphous carbon layer by using a liquid phase polymer acrylonitrile telomer (ANT) as the precursor companied with a post-annealing strategy. As a result, the rate performance, long cycling performance and high voltage performance of carbon coated NMC811 batteries are greatly improved. The insight mechanism was disclosed by advanced characterization techniques including focused ion beam, high-resolution transmission electron microscopy, scanning electron microscope, and X-ray photoelectron spectroscopy (XPS). A severe intergranular/intragranular cracking was found in bare NMC811 cathode after long-term cycling, indicating that bare NMC811 experienced serious surface phase reconstruction, oxygen release, and electrolyte decomposition. XPS results indicate that an unstable cathode electrolyte interphase (CEI) layer was formed under high voltage at the interface between bare NMC811 and the electrolyte. With the protection of amorphous carbon, the intergranular/intragranular cracking problem is alleviated, and a LiF-rich CEI layer was created at the electrode/electrolyte interface, therefore, rendering a high voltage stable and longterm cycling performance NMC811 batteries.