Redox Species-Based Electrolytes for Advanced Rechargeable Lithium Ion Batteries

Seeking high-capacity cathodes has become an intensive effort in lithium ion battery research; however, the low energy density still remains a major issue for sustainable handheld devices and vehicles. Herein, we present a new strategy of integrating a redox species-based electrolyte in batteries to boost their performance. Taking the olivine LiFePO 4 -based battery as an example, the incorporation of redox species (i.e., polysulfide of Li 2 S 8 ) in the electrolyte results in much lower polarization and superior stability, where the dissociated Li + /S x 2– can significantly speed up the lithium diffusion. More importantly, the presence of the S 8 2– /S 2– redox reaction further contributes extra capacity, making a completely new LiFePO 4 /Li 2 S x hybrid battery with a high energy 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 a rechargeable battery is an efficient and scalable approach for obtaining higher energy density storage devices.