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

Constructing a stable solid electrolyte interphase (SEI) is essential for enabling high-capacity alloying anodes in next-generation lithium-ion batteries (LIBs). However, conventional strategies based on high salt concentrations or expensive additives are limited by high cost, viscosity, and poor compatibility. Herein, we develop a solvation engineering strategy to increase the coordination number of additive molecules in the Li⁺ solvation shell by minimizing anion participation. A low-salt electrolyte composed of 0.2 M LiFSI (LiPF₆) in DMM/THF/FEC (4:3:3 by vol%) enables additive-dominated coordination and facilitates the formation of a uniform, fluorine-rich SEI. Characterizations including molecular dynamics simulations, spectroscopy, and 3D electrode reconstruction confirm this tailored solvation environment stabilizes the Si interface and mitigates volume-induced degradation. As a result, silicon anode exhibits a specific capacity of ∼2000 mAh g^-1 over 200 cycles, while graphite anodes retain 96% capacity after 500 cycles. Stable cycling performances can also be achieved in different pouch cells. This work underscores the critical importance of additive coordination control in electrolyte design and provides a broadly applicable, cost-effective strategy for advancing alloy-type anodes in practical LIB systems.