In a modified diaphragm special for a Li-S battery, the surface at one side, close to a positive
electrode, of a general diaphragm is coated with a Ketjen black coated
metal oxide modified
coating layer added with a conductive agent. A preparation method of the modified diaphragm special for the Li-S battery comprises the following steps of sequentially mixing Ketjen black and an
aqueous solution of a
metal oxide inorganic salt, carrying out dispersion,
drying and calcinations to prepare a paste, and applying the paste at one side, close to the positive
electrode, of a commercial diaphragm to obtain the modified diaphragm. The invention also discloses the Li-S battery applying the modified diaphragm special for the Li-S battery. The Li-S battery is prepared by taking
metal lithium as a negative
electrode, applying a Ketjen balck-
sulfur composite material onto an
aluminum foil to serve as the positive electrode, taking a mixture of LiTFSI,
lithium nitrate, 1,3-
dioxolane and glycol
dimethyl ether as an
electrolyte and assembling the modified diaphragm special for the Li-S battery. With the modified diaphragm disclosed by the invention, a "shuttle effect" of
polysulfide lithium in the Li-S battery can be prevented, the electrochemical performance and the capacity of the Li-S battery are improved, the cycle lifetime of the Li-S battery is prolonged, and the modified diaphragm is suitably used for production at a large scale.