The Co-free LiNi_0.5Mn_1.5O₄ (LNMO) is a promising cathode for lithium-ion batteries owing to its high operating voltage and low costs. However, the synthesis of LNMO is generally time and energy consuming, and its practical application is hindered by the lack of a compatible electrolyte. Herein, a spray pyrolysis-based energy-saving synthesis method as well as a diluted low concentration electrolyte (0.5 M LiPF₆ in a mixture of fluoroethylene carbonate/dimethyl carbonate/1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (FEC:DMC:TTE, 1:4:5 by volume)) are proposed to address these challenges. Owing to the unique features of the precursor prepared by spray pyrolysis, well-crystallized LNMO single-crystal can be obtained within 1 h calcination at 900 °C. Besides, the fluorinated interphases derived from the diluted low concentration electrolyte not only mitigate the Mn dissolution and Al corrosion at the cathode side, but also suppresses dendritic Li deposition at the anode side, thus enabling stable cycling of both LNMO and Li metal anode. Thus, 30 μm Li | LNMO (1.75 mA h cm⁻²) cells achieve a high capacity retention (90.9%) after 168 cycles in the diluted low concentration electrolyte.