Solvation-Shell Engineering Enables Additive-Dominated Coordination for Stable Silicon Anodes Under Minimal Salt...

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Stable solid electrolyte interphase (SEI) formation is critical for high-capacity alloying anodes in next-generation lithium-ion batteries (LIBs).
• Conventional SEI strategies using high salt concentrations or expensive additives face limitations such as high cost, viscosity, and poor compatibility.

Purpose of the Study:

• To develop a cost-effective and broadly applicable solvation engineering strategy for creating stable SEI layers.
• To enhance the performance and cycle life of silicon anodes in LIBs by controlling additive coordination in the Li⁺ solvation shell.

Main Methods:

• Utilized a low-salt electrolyte (0.2 M LiFSI in DMM/THF/FEC) designed to minimize anion participation in the Li⁺ solvation shell.
• Employed molecular dynamics simulations, spectroscopy, and 3D electrode reconstruction to characterize the solvation environment and SEI properties.
• Tested silicon and graphite anodes in pouch cells to evaluate cycling performance and capacity retention.

Main Results:

• Achieved additive-dominated coordination in the Li⁺ solvation shell, leading to a uniform, fluorine-rich SEI.
• Demonstrated stabilization of the silicon anode interface, mitigating volume-induced degradation and enabling a specific capacity of ~2000 mAh g⁻¹ over 200 cycles.
• Graphite anodes retained 96% capacity after 500 cycles, and stable performance was confirmed in pouch cells.

Conclusions:

• Additive coordination control within the Li⁺ solvation shell is crucial for designing effective electrolytes for advanced LIBs.
• The proposed solvation engineering strategy offers a cost-effective and broadly applicable method for advancing alloy-type anodes in practical LIB systems.