Tesla and his team of researchers from Dalhousie University, including Jeffrey Dahn were going to developed a new kind of Lithium -ion battery which can power electric vehicles a million miles and can last atleast two decades.
The team used a new type of Cathode materials called NCM523 which consist of 50% Nickle and 20% Cobalt and 30% Manganese. They choose synthetic Graphite Anode for their battery. The choose blend of lithium salt with other ionic compound as electrolyte.
The Tesla team taking a single large crystals of materials for their battery so as no crack was developed during charged and discharged cycles. Because of that this battery having a very longer life span.
Very soon Tesla was going to make this technology into a reality.
Source : https://www.theengineer.co.uk/tesla-million-mile-battery/