Designer Cathode Additive for Stable Interphases on High-Energy Anodes
Mengyu Tian, Liubin Ben, Hailong Yu, Ziyu Song, Yong Yan, Wenwu Zhao, Michel Armand, Heng Zhang, Zhibin Zhou, Xuejie Huang
Abstract
Rechargeable lithium-based batteries built with high-energy anode materials (e.g., silicon-based and silicon-derivative materials) are considered a feasible solution to satisfy the stringent requirements imposed by emerging markets, including electric vehicles and grid storage, due to their higher energy density compared to contemporary lithium-ion batteries. The robustness of the solid electrolyte interphase (SEI) layer on high-energy anodes is critical to achieve long-term and stable cycling performances of the batteries. Herein, we propose a new type of designer cathode additive (DCA), i.e., an ultrathin coating layer of elemental sulfur on the cathode, for the in situ formation of a thin and robust SEI layer on various types of high-energy anodes. The DCA elemental sulfur undergoes simultaneous oxidation and reduction paths, forming lithium alkyl sulfate (R–OSO2OLi) and poly(ethylene oxide) (PEO)-like polymers on the anode surface. The as-formed R–OSO2OLi/PEO-modified SEI layer has good lithium cation (Li+) permeability to facilitate fast ion transportation across the interphases and superior elasticity to adapt to large volume changes, which is particularly effective for improving the cycling efficiency of high-energy anodes (e.g., ca. 14–35% increase in capacity retention for the silicon–carbon composite (SiC) or silicon–tin alloy (Si–Sn)||LiFePO4 cells). The present work opens a new avenue toward the practical deployment of high-energy rechargeable lithium-based batteries.