Battery module unit, battery module, energy storage system, and electric vehicle

A battery module unit, configured to form a battery module, wherein the battery module unit comprises:

• a plurality of sequentially stacked first brackets and a plurality of battery cells, wherein each first bracket comprises a bracket body, and a battery cell is accommodated between two adjacent bracket bodies;
• the plurality of first brackets comprise at least one first fixing bracket, and the at least one first fixing bracket is disposed between other first brackets;
• at least one battery cell on one side of the first fixing bracket forms a first battery cell group;
• at least one battery cell on an other side of the first fixing bracket forms a second battery cell group;
• a connecting structure is disposed at one end of a plurality of the bracket bodies,
• a fastener is disposed on the bracket body of the first fixing bracket, and the fastener of the first fixing bracket is fixed to the connecting structure to fix the connecting structure to the first fixing bracket in a first direction, wherein the first direction is a stacking direction of the plurality of first brackets,
• the first battery cell group is symmetric to the second battery cell group around a symmetric central axis of the first fixing bracket, or the first battery cell group is symmetric to the second battery cell group around a symmetric central axis of a plurality of the first fixing brackets,
• a busbar configured to connect tabs of the battery cell, and the busbar is fixed to the connecting structure,
• a positioning pin is disposed on at least one first bracket, and a corresponding positioning hole is disposed on the connecting structure;
• and
• the positioning pin is configured to run through the corresponding positioning hole,
• wherein the positioning pin is configured to move a preset distance in the positioning hole along a direction parallel to the first direction.