Described in Nature Energy, the lithium iron phosphate (LFP) battery is able to self-heat quickly up to 60 degrees Celsius during charge and discharge, then cool quickly when not in use. It uses a thin nickel foil with one end attached to the negative terminal and the other extending outside the cell to create a third terminal. Once electrons flow, it rapidly heats up the nickel foil through resistance heating and warms the inside of the battery. As soon as the internal temperature reaches 60° C, the switch opens and the battery is ready for rapid charge or discharge.
"We developed a pretty clever battery for mass-market electric vehicles with cost parity with combustion engine vehicles," said Chao-Yang Wang, professor of chemical engineering and materials science and engineering, and director of the Electrochemical Engine Centre at Penn State.
"There is no more range anxiety and this battery is affordable."
Wang says a 40kW/h battery can generate 300kW of power, enough to take an EV from 0-60mph in around three seconds. However, a 40kW/h Nissan Leaf has a range of just 230km, so it is not clear if more than one battery would be required to enable the aforementioned 400km range.
The team modelled the battery using a combination of existing technologies and innovative approaches. They claim that the self-heating method allows for the use of relatively low-cost materials in comparison with current battery technology. The cathode is thermally stable, lithium iron phosphate and does not contain expensive and scarce materials such as cobalt, while the anode is made of very large particle graphite, a safe, light and inexpensive material.
According to the Penn State engineers, the self-heating technology also prevents uneven deposition of lithium on the anode, which can cause the dendrites that often lead to lithium-ion battery failure. It is claimed that the EV battery has a potential lifespan of around two million miles – several orders of magnitude greater than current technology.
"This battery has reduced weight, volume and cost," said Wang. "I am very happy that we finally found a battery that will benefit the mainstream consumer mass market…this is how we are going to change the environment and not contribute to just the luxury cars.”