Lithium ion cells with improved thermal stability

The present invention provides a solution to the problem of degradation of the polymeric binder material used in lithium secondary cells based on a reduction in number of active sites in the copolymer. The battery of the present invention comprises a positive electrode element, a negative electrode element, and a separator membrane element disposed between said electrode elements, at least one of said electrode elements comprising a polymeric binder intermingled with an active material, said polymeric binder comprising a copolymer of vinylidene fluoride VdF, at least one other fluorinated monomer (OFM), and cross-linking agent for said copolymer.