NOVELTY - Lithium ion battery includes at least one electrochemical battery cell (12) which comprises: a negative electrode (14); a positive electrode (16) situated opposite the negative electrode; and a physically crosslinked gel electrolyte (18) disposed between confronting faces of the negative and positive electrodes. The gel electrolyte comprises a block copolymer host and a liquid electrolyte absorbed into the block copolymer host. The block copolymer host has poly(alkylene oxide) block units and physically crosslinkable block units containing polyamide or poly(terephthalate) ester block units.    USE - The lithium ion battery is useful for providing an electrical current to an electrical device including wide variety of electrical loads and power-generating devices e.g. electric motor for a hybrid electric vehicle or an extended-range electric vehicle.    ADVANTAGE - The lithium ion battery: utilizes the block copolymer host to provide the gel electrolyte with consistent operational stability over a wide temperature operating window; and prevents a short circuit, and provides sufficient contacting interfaces to accommodate lithium ion mobility between the electrodes.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for the physically crosslinked gel electrolyte comprising: the block copolymer host that comprises poly(alkylene oxide) block units and physically crosslinkable block units, where the poly(alkylene oxide) block units establish soft domains, the physically crosslinkable block units interact with one another to establish hard domains, and the soft domains have a greater affinity for liquid electrolyte absorption than the hard domains; and the liquid electrolyte absorbed into the block copolymer host.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of the electrochemical battery cells included in the lithium ion battery along with its associated metallic current collectors.    Electrochemical battery cell (12)    Negative electrode (14)    Positive electrode (16)    Positive-side inner face (16a)    Gel electrolyte (18)