Improving the electrochemical performance of hard carbon||NaxNi1=3Mn1=3Co1=3O2 full-cell by presodiation methods

Introduction: We study the electrochemical behaviors of sol-gel NaxNi1=3Mn1=3Co1=3O2 (NaNMC) material assembled in sodium half-cell and full-cell configuration, focusing on the cycling performance. Method: The crystalline structure and the lattice parameters of synthesized NaNMC were characterized by using X-ray diffraction (XRD). The electrochemical characterization of NaNMC sample was investigated in sodium-ion half-cell by cyclic voltammogram (CV) and galvanostatic cycling with potential limitation (GCPL). To improve the reversible capacity of sodium-ion full-cell, we suggested two presodiation methods to reduce the irreversible capacity of the hard carbon before assembling full-cell: i) the chemical method and ii) the electrochemical method. Results: In the half-cell, the specific capacity of NaNMC is about 106 mAh.g-1 and well maintained 88 mAh.g-1 after 100 cycles in a potential range of 2.0 – 4.0 V. When assembling the full-cell with a pristine hard-carbon, the cell capacity of only 30 mAh.g-1 but quickly decreased after several cycles due to large irreversible capacity of hard carbon in the initial cycle. As a result, both methods significantly increased ICE (Initial Coul