Nonflammable Fluorinated Carbonate Electrolyte with High Salt-to-Solvent Ratios Enables Stable Silicon-Based Anode for Next-Generation Lithium-Ion Batteries.

High energy density and safety are two key factors for the development of next-generation lithium-ion batteries. Recently, silicon (Si) has attracted tremendous interest owing to its high theoretical capacity. However, the fast capacity decay triggered by huge volume change restricts its practical application. Moreover, higher energy density brings about more serious safety issues. To solve these problems, here we propose a safer high salt-to-solvent electrolyte that consisted of nonflammable mixture solvents of di-2,2,2-trifluoroethyl carbonate and fluoroethylene carbonate. It is revealed that this electrolyte could not only enhance the cycling stability toward the silicon nanoparticle (SiNPs) anode but also solve the safety hazards. A high initial reversible capacity of 2644 mAh g and a low capacity fading rate (only 0.064% per cycle) after 300 cycles are delivered. The performance enhancement mechanism is further explored by electrochemical impedance spectroscopy, Fourier transform infrared, and scanning electron microscopy. This study may shed an inspiring light on the development of next-generation high-energy-density batteries.