Redox Species-Based Electrolytes for Advanced Rechargeable\nLithium Ion Batteries

Abstract

Seeking\nhigh-capacity cathodes has become an intensive effort in\nlithium ion battery research; however, the low energy density still\nremains a major issue for sustainable handheld devices and vehicles.\nHerein, we present a new strategy of integrating a redox species-based\nelectrolyte in batteries to boost their performance. Taking the olivine\nLiFePO₄-based battery as an example, the incorporation\nof redox species (i.e., polysulfide of Li₂S₈) in the electrolyte results in much lower polarization and superior\nstability, where the dissociated Li⁺/S_<i>x</i>^2– can significantly speed up the lithium\ndiffusion. More importantly, the presence of the S₈^2–/S^2– redox reaction further contributes\nextra capacity, making a completely new LiFePO₄/Li₂S_<i>x</i> hybrid battery with a high\nenergy density of 1124 Wh kg_cathode^–1 and a capacity of 442 mAh g_cathode^–1. The marriage of appropriate redox species in an electrolyte for\na rechargeable battery is an efficient and scalable approach for obtaining\nhigher energy density storage devices.