NOVELTY - The module (100L) has a guide portion i.e. projecting portion, including a through-hole communicating with a gas discharge space. Another guide portion i.e. projecting portion, has a through-hole communicating with another gas discharge space. A guide portion communication component has a flexible unit i.e. L-shaped tubular rubber unit (160L), for connecting the guide portions. Each through-hole has a lowermost surface positioned lower than a set of axes of any of multiple cylindrical battery cells i.e. lithium ion battery cells, arranged in a case (110).    USE - Battery module e.g. high potential side battery module and low potential side battery module, for storing and releasing electrical energy in an electricity storage device (claimed) i.e. lithium ion battery device, of an in-vehicle power supply device for an electrically operated vehicle e.g. electric automobile such as hybrid electric automobile and pure electric automobile. Can also be used for railroad vehicle i.e. hybrid train, public transport vehicle i.e. bus, cargo vehicle i.e. lorry, and industrial vehicle i.e. battery type fork lift truck, and for an uninterruptible power supply device of a computer system or a server system and for an electricity generation facility for a home.    ADVANTAGE - The through-hole has the lowermost surface positioned lower than the axes of any of the cylindrical battery cells arranged in the case, so that a gas including liquid in mist form can be smoothly discharged from the gas discharge spaces into the through-holes, thus preventing the gas from stagnating upon a gas discharge path. The gas discharge spaces are defined between a pair of side plates and a pair of covers so as to avoid the need for a safety valve for each cell, thus performing connection among the cells and the gas discharge spaces in a simple and easy manner, and hence enhancing working convenience of the module. The module uses a set of electrically conductive elements fitted to the side plates from exterior of the case, thus establishing a set of connections among the electrically conductive elements and the cells in a simple and easy manner. The through-holes are formed in the side plates and positioned to correspond to the cells, where a pair of annular grooves is formed in the side plates for ensuring thickness of a set of adhesive mass that adheres the cells to the side plates. The projecting portions and the gas discharge device are provided within a set of recessed portions such that the module is more compact, thus ensuring that a gas discharge device is prevented from impeding a fitting task when the module or the electricity storage device is fitted to the vehicle. The module has a set of bellows portions provided at a pair of ends of the tubular rubber unit to absorb variation of distance between the projecting portions by extension and retraction of the bellows portions, so that the fitting task is simple and easy.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for an electricity storage device comprising an external communication element.    DESCRIPTION OF DRAWING(S) - The drawing shows a partial perspective view of an electricity storage device.    Battery module (100L)    Case (110)    L-shaped tubular rubber unit (160L)    T-shaped shaped coupling (170)    L-shaped shaped coupling (190)