Focusing on the Subsequent Coulombic Efficiencies of SiOx: Initial High-Temperature Charge after Over-Capacity Prelithiation for High-Efficiency SiOx-Based Full-Cell Battery.

Abstract

SiOx-based anode materials are considered to be promising and have been gradually commercialized due to their high specific capacity as well as the acceptable volume change during lithiation/delithiation and preferable cycling stability compared to that of Si. Nevertheless, their inherently low Coulombic efficiency hinders the large-scale application. Up to now, researchers have paid much attention to the initial Coulombic efficiency and developed a series of effective prelithiation strategies. However, the subsequent cycles (focusing on the 2nd to 10th), during which the SiOx anode suffers great lithium consumption as well, have received scarcely any concerns. In this work, a strategy of high-temperature (50 °C) initial charge after an overcapacity prelithiation for a SiOx-based full-cell battery is proposed. As high temperature can promote the reaction between lithium and the SiO2 matrix of SiOx, SiO2 will experience a one-step thorough reduction rather than gradual conversion in subsequent cycles, improving the subsequent Coulombic efficiencies (SCEs) accordingly. Overcapacity prelithiation can be achieved safely at 50 °C without Li metal depositon, just enough to meet the more initial lithium demand of anode at 50 °C. Furthermore, the initial deeper reduction of SiO2 will release extra Si, improving the reversible capacity consequently. With the 50 °C initial charge after an overcapacity prelithiation, the full-cell battery exhibits considerable capacity retention as expected. This work raises concerns on SCEs of SiOx-based anode innovatively, providing a feasible avenue for improving the capacity retention of a SiOx-based full-cell battery.