Building a Better EV Battery
Updated February 7, 2017
Automakers might want to take note of a couple of new developments in rechargeable battery technology. Researchers at University of California San Diego [UCSD] and NEC Corp have been working on two different improvement to the same product, the Lithium-ion [Li-ion] rechargeable battery pack. Imagine if they worked together!
At UCSD, Professor Miroslav Krstic and postdoctoral fellow Scott Moura have been working to better their understanding of how Li-ion rechargeable batteries work at the molecular level. They have developed algorithms that control how the battery cycles, that is, how it charges and discharges. Current EV and HEV batteries only cycle 20%-80% to maintain maximum lifespan, so they’re basically 40% larger than they could be.
According to Krstic, current battery-evaluation by voltage and current measurements are simply too crude to use the battery to its full potential. “If one could have a better knowledge or better estimation of what’s going on inside, one could [safely] operate closer to the limits of performance, which means that the oversizing and overdesign would be less necessary,” Krstic said, “which translates into savings in costs and in weight.” Otherwise, it could mean a boost in efficiency, power, and range.
NEC has been working on a materials change in their Li-ion battery design. By substituting nickel for part of the manganese, they were able to create a higher voltage anode, which when combined with graphite and a modified version of their previous polycarbonate-based electrolyte, raised the voltage of the individual cell from 3.8V to 4.5V, which may not seem like much, but on a larger scale, this could mean a substantial increase in EV range.
The old Li-ion battery had an energy density of 150Wh/kg and the new formulation increases that to over 200Wh/kg, about 30% difference. The new materials also function better at higher temperatures, which could mean faster recharge times. Since 2009, Nissan and NEC have been working together to build a longer-range EV battery. This could be what they were working on.
The biggest hurdle to EVs hitting the mainstream is not their form, it’s their function. Limited range and excessive recharge times are the problems the EV industry has been contending with, and their sales figures have reflected this. If NEC and UCSD got together, the sum of their efforts could effectively double current EV range technology and change the market.
The Nissan Leaf, for example, has a factory range of 73 miles. UCSD’s cycle-control algorithms could mean changing from a 20-80% cycle to a 5-95% cycle, effectively increasing the usable range to 109 miles using the same battery pack. If Nissan replaced their current battery pack with NEC’s new battery technology could add 30% range with the same weight, or about 95 miles total range.
Combining forces, however, using NEC’s new battery, governed by UCSD’s cycle controls, could mean a total range of 142 miles, nearly double the current range. Add to this faster recharging times, and you’ve got a recipe for changing the future of EV technology and the EV market.
Categories: New Cars