Electrolyte solvation chemistry has attracted great attention since the recent discovery of its effect on the performances of metal-ion batteries. However, it is challenging to discern its decisive influence from the well-known effect of the solid electrolyte interphase (SEI) layer. This issue becomes more complex upon introducing additives into the electrolyte, as the key role of additives in forming the SEI layer or changing the electrolyte solvation structure also become hard to be discerned. Herein, we design a new dimethyl ether-based electrolyte, and then we unravel the effects of solvation chemistry and the SEI on determining electrode performances, such as the antimony (Sb) anode as a promising example for lithium-ion batteries (LIBs). We find that both the unique solvation structure-derived interfacial model and the SEI are necessary to stabilize the Sb anode. The influences of electrolyte components, particularly the lithium difluoro(oxalato)borate additive, were elucidated for the first time by the dynamic molecular behaviors ranging from solvation structure, interfacial model, to microstructure of the SEI. Finally, extremely high performance of the Sb anode with the capacity of 668 mAh g–1, high-rate performance over 5 A g–1, and long cycle life over 100 cycles are obtained, which is superior to that previously reported. This work provides a comprehensive guideline for designing electrolytes via a synergetic approach of solvation structure and the SEI aspects.