Construction of a Robust Solid Electrolyte Interphase on Ge Anode to Achieve a Superior Long-Term Cycle Life of Lithium-Ion Battery

Abstract

Alloy-based materials are suffering a huge volume expansion/shrink during the repeat lithium-ion intercalation/deintercalation process, so they always display an unsatisfied electrochemical performance, especially for the cycle life. In this work, we design a localized highly concentrated electrolyte (LHCE) for Ge anode, by dissolving LiFSI in DME/TTE (3:7 by volume). Raman spectra illustrate that most FSI- anions in LHCE coordinate with Li+ ions, producing the solvated structure in form of AGGs or CIPs. XPS spectra prove that the solid electrolyte interphase (SEI) derived from such a solvation structure is rich in inorganic phase, such as Li2CO3, Li3N and LiF. So the SEI is more stable and thinner, and it can keep the integrity of Ge particles and avoid their crushing during a long-term cycle. Although a serious capacity decrease at around the 30th cycle is found in esters electrolytes, the similar phenomenon is never seen in LHCE. The PM-550@Ge in LHCE remains a reversible capacity of 1040 mAh g-1 after 300 cycles at 0.5 A g-1, and the capacity retention ratio is as high as 84%. Even after a long cycling of 500 cycles, the PM-550@Ge delivers a high reversible capacity of 951 mAh g-1 at 1.0 A g-1.

Keywords: FSI- anions derived SEI, Solvation structure, Long-term cycling, Ge anode, Lithium-ion battery