A method of purifying an organic solvent, comprising: passing the organic solvent through a first filter unit, a second filter unit, a third filter unit, and a fourth filter unit to obtain a purified organic solvent, wherein the second filter unit is downstream of the first filter unit, the third filter unit is disposed between the first and second filter units, and the fourth filter unit is downstream of the second filter unit; wherein the first filter unit comprises a first housing and at least one first filter in the first housing, and the first filter comprises a filtration medium having a first average pore size; wherein the second filter unit comprises a second housing and at least two second filters in the second housing, the at least two second filters are arranged in the second housing in parallel, and each of the second filters independently comprises a filtration medium having a second average pore size; wherein the third filter unit comprises a third housing and at least one third filter in the third housing, the at least one third filter comprises a filtration medium having a third average pore size, and the filtration medium in the at least one third filter comprises an ion exchange membrane; wherein the fourth filter unit comprises a fourth housing and at least two fourth filters in the fourth housing, the at least two fourth filters are arranged in the fourth housing in parallel, and each of the fourth filters independently comprises a filtration medium having a fourth average pore size; and wherein the number of the first filter in the first filter unit is smaller than the number of the second filters in the second filter unit, the first average pore size is larger than the second average pore size, the number of the first filter in the first filter unit is smaller than the number of the third filter in the third filter unit, the number of the second filters in the second filter unit is smaller than the number of the fourth filters in the fourth filter unit, and the fourth average pore size is smaller than the second average pore size. passing the organic solvent through a first filter unit, a second filter unit, a third filter unit, and a fourth filter unit to obtain a purified organic solvent, wherein the second filter unit is downstream of the first filter unit, the third filter unit is disposed between the first and second filter units, and the fourth filter unit is downstream of the second filter unit; wherein the first filter unit comprises a first housing and at least one first filter in the first housing, and the first filter comprises a filtration medium having a first average pore size; wherein the second filter unit comprises a second housing and at least two second filters in the second housing, the at least two second filters are arranged in the second housing in parallel, and each of the second filters independently comprises a filtration medium having a second average pore size; wherein the third filter unit comprises a third housing and at least one third filter in the third housing, the at least one third filter comprises a filtration medium having a third average pore size, and the filtration medium in the at least one third filter comprises an ion exchange membrane; wherein the fourth filter unit comprises a fourth housing and at least two fourth filters in the fourth housing, the at least two fourth filters are arranged in the fourth housing in parallel, and each of the fourth filters independently comprises a filtration medium having a fourth average pore size; and wherein the number of the first filter in the first filter unit is smaller than the number of the second filters in the second filter unit, the first average pore size is larger than the second average pore size, the number of the first filter in the first filter unit is smaller than the number of the third filter in the third filter unit, the number of the second filters in the second filter unit is smaller than the number of the fourth filters in the fourth filter unit, and the fourth average pore size is smaller than the second average pore size.