Regulating the Solvation Structure of Li+ Enables Chemical Prelithiation of Silicon-Based Anodes Toward High-Energy Lithium-Ion Batteries

Highlights By selecting 4-methylbiphenyl as an anion ligand and 2-methyltetrahydrofuran as a solvent, the as-prepared micro-sized SiO/C anode can achieve an initial Coulombic efficiency of ~100%. Molecular dynamics simulations demonstrate that the ideal prelithiation efficiency can be achieved by choosing appropriate anion ligand and solvent to regulate the solvation structure of Li+. The positive effect of pre-lithiation on cycle performance has been verified by using an in-situ electrochemical dilatometry and solid electrolyte interphase film. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-023-01068-8.


S1.1 Half-Cell Assembly and Electrochemical Measurements
The electrochemical performances were characterized by assembling CR2032 coin cells with lithium foil as the counter electrode and (prelithiated) anode as working electrode.1M LiPF6 EC/DEC (1:1 v/v) electrolyte with 5 vol% FEC was used as the electrolyte.Galvanostatic charge/discharge measurements were performed in a potential range of 0.01-2.0V using a multichannel battery testing system (LAND CT2001A).Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were tested with electrochemical workstation system (Biologic Science Instruments, Claix, France).

S1.2 Full-Cell Assembly and Electrochemical Measurements
SiO/C and p-SiO/C were used as anodes and high voltage LiCoO2 (LCO) were used as cathode.The mass ratio of cathode to anode was around 3:1, and the weight ratio of LCO: carbon black: PVDF was 8:1:1 in the cathode.The full-cells were galvanostatic charged/discharged at 0.1 A g -1 in the electrochemical window of 3-4.35 V.
The electrolyte used in CV tests was 1 M LiPF6 in THF/2-MTHF solvent containing 0.1 M Li-arene.The Cu foil and lithium metal were used as the counter electrode and as working electrode, respectively.CV curves were recorded at a scanning rate of 20 mV s -1 at room temperature.
The average solvation structure around a lithium cation is determined by the integrated radial distribution function analysis (coordination number) of a MD trajectory.On that basis, the solvation strucutures are extracted from the three MD simulations.Subsequently, the structures are optimized at the B3LYP-D3/6-31+G* level of theory, and further calculated at the B3LYP-D3/6-311G** level of theory.The electrostatic potential as well as the molecular isosurface are analyzed by Multiwfn and visualized by VMD program.The construction of SEI film during the prelithiation process can compensate for Li + loss and solve the solid-liquid interface problem, which is an effective means to achieve stable cycle and high capacity retention.As shown in Fig. S6, the thermodynamic stability of the solid-liquid interface depends on the energy difference between the Fermi level of anode and the electrolyte LUMO level.When the LUMO energy level of the electrolyte is lower than the electrochemical potential (μA) of the negative electrode, the electrolyte will spontaneously reduce and consume Li + , resulting in the passivation of the electrode surface to form a SEI film.

Fig. S1
Fig. S1 (a-b) SEM images and (c) XRD pattern of the SiO/C particles Fig. S1 (a-b) SEM images and (c) XRD pattern of the SiO/C particles

Fig. S7
Fig. S7 TEM images of p-SiO/C anodes (a, c) before and (b, d) after 100 cycles