Optimizing the potential of intercalation on anode for long-cycle 420 Wh/kg Li-ion batteries

Abstract

Utilization of novel cathode and anode materials is expected to achieve ultrahigh energy density of Li-ion batteries, but it usually suffers from a large capacity fade in full cells. Here we propose a strategy towards optimizing reversibility of intercalation/deintercalation in anode via regulating the negative/positive capacity ratio (N/P) ratios in full cells with Li-rich layered oxide cathode and SiOx@graphite anode. Compared with high N/P ratio, the cell with an optimal N/P ratio of 0.90 displays the best cycling performance. Some comprehensive characterizations such as in-situ pressure and electrochemical measurements reveal that the lower N/P ratio could reduce the polarization on this composite anode to maximize the utilization of the graphite component and minimize the irreversible pressure growth. On the basis of unraveled failure mechanisms, a 21 Ah multilayer pouch cell with low N/P ratio delivers the energy density up to 420 Wh kg−1 based on total mass of the cell and the capacity retention retains 82% after 300 cycles at 0.2 C. This work highlights the strong coupling between cell parameters and electrochemical performances, providing a new insight towards the dominant factor for irreversible Li-ion behavior during cycling besides the structural degradation of materials for high-energy-density Li-ion batteries.