A battery module, comprising: - a housing; - a plurality of battery cells disposed in the housing; and - a bus bar configured to electrically couple two adjacent battery cells of the plurality of battery cells, wherein the bus bar comprises: - a first end coupled to a first terminal of a first battery cell of the plurality of battery cells, wherein the first end is formed from a first material, and wherein the first end comprises a first collar extending from a lower surface of the bus bar configured to receive and surround the first terminal; - a second end coupled to a second terminal of a second battery cell of the plurality of battery cells, wherein the second end is formed from a second material, and wherein the second end comprises a second collar extending from the lower surface of the bus bar configured to receive and surround the second terminal, wherein the first and second materials are different materials, and wherein the lower surface of the bus bar faces the first battery cell and the second battery cell, when the bus bar is electrically coupled to the first terminal and the second terminal; and - a joint disposed between the first end and the second end, wherein the joint mechanically and electrically couples the first end to the second end, wherein the joint comprises a rolled finger joint. - a housing; - a plurality of battery cells disposed in the housing; and - a bus bar configured to electrically couple two adjacent battery cells of the plurality of battery cells, wherein the bus bar comprises: - a first end coupled to a first terminal of a first battery cell of the plurality of battery cells, wherein the first end is formed from a first material, and wherein the first end comprises a first collar extending from a lower surface of the bus bar configured to receive and surround the first terminal; - a second end coupled to a second terminal of a second battery cell of the plurality of battery cells, wherein the second end is formed from a second material, and wherein the second end comprises a second collar extending from the lower surface of the bus bar configured to receive and surround the second terminal, wherein the first and second materials are different materials, and wherein the lower surface of the bus bar faces the first battery cell and the second battery cell, when the bus bar is electrically coupled to the first terminal and the second terminal; and - a joint disposed between the first end and the second end, wherein the joint mechanically and electrically couples the first end to the second end, wherein the joint comprises a rolled finger joint. - a first end coupled to a first terminal of a first battery cell of the plurality of battery cells, wherein the first end is formed from a first material, and wherein the first end comprises a first collar extending from a lower surface of the bus bar configured to receive and surround the first terminal; - a second end coupled to a second terminal of a second battery cell of the plurality of battery cells, wherein the second end is formed from a second material, and wherein the second end comprises a second collar extending from the lower surface of the bus bar configured to receive and surround the second terminal, wherein the first and second materials are different materials, and wherein the lower surface of the bus bar faces the first battery cell and the second battery cell, when the bus bar is electrically coupled to the first terminal and the second terminal; and - a joint disposed between the first end and the second end, wherein the joint mechanically and electrically couples the first end to the second end, wherein the joint comprises a rolled finger joint.