Enhancing Cycle Stability of Li/VS4 Batteries with Localized High-Concentration Carbonate-Based Electrolytes

Abstract

Vanadium sulfide (VS4) is a promising cathode material for rechargeable lithium batteries because of its high theoretical capacity (1197 mAh g−1).1 However, this cathode material suffers from low Coulombic efficiency and fast capacity fading during battery cycling. Here we report a localized high-concentration electrolyte composed of lithium bis(fluorosulfonyl)imide (LiFSI), ethylene carbonate (EC), propylene carbonate (PC), and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (HFE) that enhances Coulombic efficiency and cycle stability of Li/VS4 batteries. A spectroscopic analysis reveals that the localized high-concentration LiFSI/EC:PC:HFE electrolyte has a local coordination state similar to that in the high concentration LiFSI/EC:PC electrolyte, which inhibits the dissolution of vanadium from VS4 during discharge/charge cycling. The inhibited vanadium dissolution should be one of the reasons for the superior stability of this cathode. This work sheds light on the design of electrolytes for stable Li/transition metal sulfides batteries.AcknowledgementThis work was supported by the New Energy and Industrial Technology Development Organization (NEDO) under the “Research and Development Initiative for Scientific Innovation of New Generation Batteries 2 (RISING2) (JPNP16001)”.Reference1. K. Koganei, A. Sakuda, T. Takeuchi, H. Sakaebe, H. Kobayashi, H. Kageyama, T. Kawaguchi, H. Kiuchi, K. Nakanishi, M. Yoshimura, T. Ohta, T. Fukunaga, E. Matsubara, Solid State Ionics 323, 32–36 (2018).