A kind of lithium ion battery

The present invention provides a kind of lithium ion battery, including shell, cover plate, electrolyte and pole piece, pole piece is drawn the first lug and the second lug；Connecting on pole piece and have a short-circuit protection assembly, short-circuit protection assembly is three-decker, including being positioned at the conductive layer of centre and being positioned at the insulating barrier of conductive layer both sides；One end of conductive layer electrically connects with the first lug of pole piece, and the other end is free end；The outmost turns collector of pole piece is the collector at the second lug place.The lithium ion battery that the present invention provides; by arranging short-circuit protection assembly on inside battery pole piece; battery is when by external force generation abnormal deformation; the large area short circuit that the complicated short-circuit conditions that can actively make inside battery is converted between positive/negative collector; internal short-circuit of battery heat is made to be reduced to minimum; heat conduction path can be shortened simultaneously, while the battery heat production speed that slows down, also increase the heat radiation time of battery, increase battery safety and reliability under the conditions of severe use.