Fluorination of free lithium residues on the surface of lithium nickel cobalt aluminum oxide cathode materials for lithium ion batteries

Lithium nickel cobalt aluminum oxide (LNCA) cathode materials for lithium ion batteries (LIBs) were treated with NH4FHF to convert free Li2CO3 and LiOH, which are natively present on the LNCA surface, into a stable LiF layer. Gas evolution caused by a side-reaction between the reactive free lithium compounds and electrolyte was greatly reduced using this method. The pH of the water dispersion of LNCA was also lower; this indicates that LiOH, which causes rapid polymerization of the polyvinylidene fluoride binder in the slurry for electrode casting, was effectively eliminated. No significant decrease of the electrochemical performance of LNCA was observed with the treatment. Designed as a one-step simple wet process, the developed method is expected to be practically applicable for mass production with suppressed swelling of LIBs and stabilization of the electrode fabrication process. (C) 2016 Elsevier Ltd. All rights reserved.