Development　of　ionic　liquid　electrolytes　(ILEs)　plays　a　key　role　in　achieving　high　safety　and　high　energy　density　in　lithium　metal　batteries.　While　introducing　cosolvents　can　reduce　the　viscosity　of　ILEs　and　enhance　Li+　transport　ability,　the　impact　of　the　solvating　ability　of　cosolvents　on　the　solvation　structure　of　ILEs　remains　unclear.　In　this　work,　we　rationally　design　the　solvating　ILEs,　with　different　solvation　abilities　of　cosolvents,　and　reveal　the　correlation　between　solvation　structure　and　electrochemical　performance.　We　found　that　introducing　cosolvents　with　moderate　solvating　ability,　such　as　ethyl　acetate　(EA),　into　the　ionic　liquid　electrolyte　can　regulate　the　solvation　structure　of　ILEs,　thereby　optimizing　Li+　transport　ability　and　enhancing　the　stability　of　the　electrode/electrolyte　interface.　With　our　designed　ionic　liquid　electrolytes　(ILEs),　the　Li||Ni0.8Co0.1Mn0.1O2　battery　cell　demonstrates　exceptional　capacity　retention　of　84.8%　after　800　cycles　at　1.0C,　significantly　outperforming　the　battery　with　a　conventional　ester　electrolyte,　which　retains　only　22.1%　capacity.　This　study　provides　practical　solutions　and　foundational　guidance　for　the　rational　design　of　advanced　ionic　liquid　electrolytes　and　the　selection　of　cosolvents,　advancing　the　development　of　high-safety　and　high-energy-density　LMBs.　©　2025　American　Chemical　Society.