Effect of scandium doping on the structural properties and electrochemical performance of nickel-rich cathode precursor of lithium ion-battery

Abstract

One of the research interests in using nickel-rich Ni0.8Mn0.1Co0.1O2 (NMC 811) battery is enhancing its cycle stability by cathode material doping. In this study, 2.5 %, 5 %, and 7.5 % mol of scandium were added to NMC-based cathode precursors and its impacts on the structural properties of the cathode precursor and electrochemical performance of the cells were investigated. Sc with 3+ valence will replace the Co in the Ni lattice. Similar to the role of Co in the NMC system, it is expected that Sc will also improve the structural stability of Ni by preventing the cation mixing in the crystal lattice. XRD analysis of the synthesized NMC 811 and Sc-doped NMC revealed a hexagonal crystal structure for both cathode precursors. The addition of an Sc dopant increases the crystallite and particle sizes of the synthesized precursors. The particle morphology of un-doped cathode precursor identified by SEM was rounded, while Sc-doped NMC is polygonal and agglomerated. Charge-discharge test results for 100 cycles demonstrated that Sc doping to NMC cathode increases cell capacity retention. The highest capacity retention of 87.54 % was found in the NMC-7.5 % Sc sample at the 100th cycle. The Sc addition dosage did not increase above 7.5 % mol since a higher Sc doping reduces the initial capacity of the cell. The EIS measurement after 100 cycle of charge-discharge test indicated the best conductivity and lithium ion diffusion values were obtained for NMC-7.5 % Sc sample, which were 4.61 × 10−07 S/cm and 3.92 × 10−10 cm2/s, respectively.