Upper insulation sheet

The utility model relates to an upper insulation sheet which is characterized in that the upper insulation sheet is a slice with the shape matched with that of the cross section of an inner cavity of a lithium battery, a flat and long positive lug through hole is formed in the middle of the slice, a plurality of bypass holes distributed around the positive lug through hole in a U shape are formed in positions close to the outer edge of the slice, electrolyte can permeate through the bypass holes, and a central auxiliary hole through which the electrolyte can permeate is formed in one side, far away from a U-shaped opening, of the positive lug through hole. The utility model aims to provide the upper insulation sheet which can be used for effectively preventing a danger of short circuit due to the contact between a positive lug and an electric core or a steel shell and can enable the electrolyte to uniformly permeate into the electric core.