A breakthrough in Coulombic reversibility of dual-ion batteries at quick charge and underlying mechanisms

Abstract

Dual-ion batteries (DIBs) with renewable graphite as cathode materials have emerged as promising alternatives to Li-ion batteries because of their sustainability and cost-effectiveness. However, DIBs still suffer from the low initial Coulombic efficiency and rapid capacity fading upon long-term cycling due to the intense co-intercalation and oxidative decomposition of electrolytes along with the anions intercalation into graphite at high potentials. To mitigate the electrolyte reactions, the common strategies are mainly focused on the optimization of electrolyte components and surface modification of graphite particles to construct superior cathode/electrolyte interphases (CEI). This work innovatively discovers and reveals that the CEI structure and electrochemical reversibility of Li||graphite DIBs can be optimized through simply adjusting the charge rates. The initial Coulombic efficiency is increased to a very high value of 90.6 % (at the charge rate of 2C), in sharp contrast with the value of 40.8 % (at the charge rate of 0.1C). Besides, the overall electrochemical performances including the reversible capacity, cycling stability and high-rate capability are all improved significantly. These results not only provide an easy strategy for the performance improvement of DIBs but also shed light on the correlation among the charge rates, electrochemical reversibility and CEI of DIBs.