Cartridge for secondary battery

A cartridge for a secondary battery, comprising:

• a lower cartridge having a side wall;
• an upper cartridge capable of being assembled with the lower cartridge;
• at least one secondary battery between the lower cartridge and the upper cartridge;
• a cell guide unit extending from the lower cartridge, the cell guide unit having two inner wall surfaces that protrude upward in at least one corner area of the lower cartridge and are adjacent to each other at right angles to each other, a height of the cell guide unit being greater than a height of the lower cartridge side wall;
• and
• a cell guide assembly unit extending from the upper cartridge, the cell guide assembly unit having a shape fit for the cell guide unit;
• wherein the cell guide unit has a lower end part and an upper end part, the upper end part having a height greater than the lower end part to create a step from outside to inside of the cell guide unit such that the upper end part of the cell guide unit is thinner than the lower end part of the cell guide unit.