NOVELTY - A cover assembly for Lithium-ion battery container comprises cover for sealing top opening of container, where cover defines opening for current collecting posts; current collecting post having gap; top flange disposed to be opposed to and displaced from top surface of cover and extending radially outward from post to beyond edges of opening; bottom flange disposed to be opposed to and displaced from cover bottom surface and extending radially outward from post to beyond edges of opening; and first polymer body which is continuous and filling gaps between cover, post, flanges.    USE - As cover assembly for a Lithium-ion battery container (claimed) used for long term applications such as home energy storage applications or electric and hybrid electric vehicles applications; and in large scale energy storage systems or high power applications such as electric and hybrid electric vehicles that require long service life and continuous high power capabilities.    ADVANTAGE - The cover assembly for a lithium-ion battery container improves the durability of the battery. The cover assembly provides high durability lithium ion batteries. The method of making the cover extends the service life of the resultant battery. With proper structure and methods being implemented in the battery container cover, durable lithium ion batteries having extended service life (targeted as 20 years) are formed.    DETAILED DESCRIPTION - A cover assembly for a Lithium-ion battery container comprises a cover for sealing a top opening of a battery container, where the cover defines at least one opening for current collecting posts; a current collecting post extending through each opening and having a gap between the current collecting post and the cover; a top flange encircling each current collecting post, disposed to be opposed to and displaced from a top surface of the cover and extending radially outward from the current collecting post to beyond edges of the opening; a bottom flange encircling each current collecting post, disposed to be opposed to and displaced from a bottom surface of the cover and extending radially outward from the current collecting post to beyond edges of the opening; and a first polymer body for each current collecting post, where the first polymer body is continuous and extends to fill all gaps formed between any of the cover, current collecting post, top flange and bottom flange, and the first polymer body is fused to the cover, current collector post, top flange and bottom flange where contacting same. The cover assembly further comprises insulating material on a bottom surface of each bottom flange, for electrically insulating each bottom flange from other components of the battery; welded seal between each current collecting post and its top flange; a second polymer body covering and fused to a top surface of the first polymer body and the surface of the top flange, including the junction interface of the first polymer body and the top flange. An INDEPENDENT CLAIM is included for method of fabricating a cover assembly for a lithium-ion battery container involving providing a cover for sealing a top opening of a battery container, where the cover defines at least one opening for current collecting post; providing a current collecting post extending through each opening and having a gap between the current collecting post and the cover; providing a first polymer body by injection molding a polymer to fill both of the gaps, and provide a polymer coating to both top and bottom surfaces of the cover at portions of the cover surrounding the current collecting posts, where the first polymer body is fused to the cover and current collecting post where contacting same; providing a top flange encircling each current collecting post and extending radially outward from the current collecting post to beyond edges of the opening, the top flange being disposed to be in contact with the first polymer body on the top surface of the cover; providing a bottom flange encircling each current collecting post and extending radially outward from the current collecting post to beyond edges of the opening, where the bottom flange is disposed to be in contact with the first polymer body on the bottom surface of the cover; and applying pressure to the top and bottom flange of each current collecting post to fuse each flange to the first polymer body.    DESCRIPTION OF DRAWING(S) - The figure shows top view of container cover.