Provided are an electrolyte solution, a positive electrode, and a lithium-ion battery containing the electrolyte solution and/or the positive electrode. The electrolyte solution comprises a lithium salt, an electrolyte solvent, and an additive, wherein the additive is an aniline compound having a structure of Formula 1 or a derivative thereof: in which R 1 and R 2 are each independently selected from at least one of -H, -(CH 2 ) n1 CH 3 , and -(CH 2 ) n2 CF 3 , where 0 ‰¤ n1 ‰¤3, and 0 ‰¤ n2 ‰¤ 3; and M 1 -M 5 are each independently selected from at least one of -H, -F, -Cl, -Br, -(CH 2 ) n3 CH 3 , and R 3 -S-R 4 , where 0 ‰¤ n3 ‰¤ 3, and at least one of M 1 -M 5 is selected from a thioether group R 3 -S-R 4 , where R 3 is selected from -(CH 2 ) n4 -, in which 0 ‰¤ n4 ‰¤1, and R 4 is selected from one or two of an aniline group or -(CH 2 ) n5 CF 3 , where 0 ‰¤ n5 ‰¤3. By adopting the aniline compound having a structure of Formula 1 or a derivative thereof as a specific additive in the present invention, the positive electrode is protected from being damaged, and the electrolyte solvent is protected from being oxidized and decomposed at a high voltage, thereby increasing the service life of a battery at a high voltage.