Square battery and related assembly method

The invention provides a square battery and a related assembly method, and relates to the field of lithium batteries. The square battery comprises a shell, an electrode terminal assembly, an adapter piece, a support, a battery cell and a bottom cover plate, the shell is provided with a containing cavity, a stepped hole and an opening, the opening and the stepped hole are communicated with the containing cavity, the opening is located at the first end of the containing cavity, the stepped hole is located at the second end of the containing cavity, and the electrode terminal assembly is fixedly connected with the shell. The electrode terminal assembly is provided with an abutting portion which abuts against the step of the step hole. The adapter plate is electrically connected with the electrode terminal assembly; the bracket is clamped between the adapter plate and the shell, and the electrode terminal assembly is arranged on the bracket in a penetrating manner; the battery cell is electrically connected with