Electrode assembly, sealed secondary battery cell, battery pack and methods

A battery pack comprising a population of secondary battery cells chargeable between a charged state and a discharged state, and a frame to hold secondary battery cells in the battery pack, wherein

• (a) members of the secondary battery cell population have a rated capacity and comprise a hermetically sealed enclosure and an electrode assembly within the hermetically sealed enclosure,
• (b) the electrode assembly has substantially polyhedral shape mutually perpendicular transverse, longitudinal and vertical axes corresponding to the x, y and z axes, respectively, of an imaginary three-dimensional Cartesian coordinate system,
• (c) the electrode assembly comprises opposing longitudinal surfaces that are substantially flat and are separated from each other in the longitudinal direction, and a lateral surface surrounding an electrode assembly longitudinal axis AEA and connecting the opposing longitudinal end surfaces, the lateral surface having opposing vertical surfaces that are substantially flat and are separated from each other in the vertical direction on opposing vertical sides of the longitudinal axis, and opposing transverse surfaces that are substantially flat and are separated from each other in the transverse direction on opposing transverse sides of the longitudinal axis,
• (d) the electrode assembly further comprises an electrode structure population, an electrically insulating separator population, and a counter-electrode structure population, wherein members of the electrode structure, electrically insulating separator and counter-electrode structure populations are arranged in an alternating sequence in the longitudinal direction within the electrode assembly,
• (e) wherein the frame holds a cell array comprising a subset of the population of secondary battery cells that are arranged adjacent to one another, with the members being arranged in the cell array such that opposing vertical surfaces of adjacent members in the cell array face each other to form an adjacent facing pair of vertical surfaces, each adjacent facing pair of vertical surfaces in the cell array comprising adjacent facing regions thereof, and
• (f) wherein the adjacent facing regions of each adjacent facing pair of vertical surfaces in the cell array are separated by less than 1 mm from each other in the vertical direction, and are in thermal contact with one another via a thermally conductive pathway having thermally conductive material that has a thermal conductivity of at least 1 W/mK,
• (g) the battery pack further comprises a cooling tube to cool the cell array, and
• (h) wherein the cell array comprises opposing cell array end surfaces separated from each other in the vertical direction, and wherein the cooling tube extends in a direction orthogonal to the vertical direction and along at least one of the opposing cell array end surfaces of the cell array to cool the at least one opposing cell array end surface.