Secondary batteries are highly applicable to a wide range of products and have electrical characteristics with high energy density. Such secondary batteries are applied not only to portable electronic devices but also to electric vehicles, hybrid vehicles, and electric power storage devices, driven by electric driving sources.
A battery pack applied to an electric vehicle and the like is configured so that a plurality of battery modules, each having a plurality of battery cells, are connected to obtain a high output. Each battery cell may be repeatedly charged and discharged by an electrochemical reaction among components including a positive electrode current collector, a negative electrode current collector, a separator, an active material, an electrolyte and the like.
Meanwhile, along with an increased need for a large capacity structure and utilization as energy storage sources in recent years, there is a growing demand for a multi-module battery pack in which a plurality of battery modules, each having a plurality of secondary batteries connected in series or in parallel, are aggregated.
Generally, a battery module applied to a battery pack is configured by stacking a plurality of battery cells and then connecting the plurality of battery cells in series or in parallel.
For the electric connection of the battery cells, electrode leads of the battery cells may be bent in any direction and then coupled to each other by welding. Generally, the plurality of battery cells are disposed side by side in one direction. At this time, the electrode leads of the battery cells are also disposed side by side in one direction at any surface of the battery cells. After that, the electrode leads are coupled in an upper or lower space of one surface of the battery cells. In this case, in order to couple the plurality of electrode leads, a separate space (the upper or lower space of the battery cells) is required for coupling the electrode leads to the battery module, and this space occupies a certain volume in the battery module, which is disadvantageous in terms of the energy volume efficiency of the battery module.