An ion-exchange strategy to eliminate anion impurities within LDH structure for refined NCA cathode materials†
Abstract
The Ni-rich NCA precursor (Ni0.80Co0.15Al0.05(OH)2), synthesized via co-precipitation using sulfate salt, contains anions such as SO42− within the layered double hydroxide (LDH) structure to compensate for the high oxidation state of Al3+. In particular, the inserted anions can deteriorate the performance of cathode materials by generating Li2SO4 during calcination, which induces particle agglomeration and disrupts the formation of a crystal structure. In this study, we explored an ion-exchange strategy using chloride ions to remove sulfate ions, since chloride ions easily volatilize during calcination. As a result, the synthesized NCA cathode represents superior rate capability and capacity retention by decreasing resistance, retaining a well-ordered crystal structure, and suppressing side reactions. These results underscore the importance of anion control in Ni-rich cathode materials with the LDH structure.