WASHINGTON, Jan. 20, 2016 - Controlling surface chemistry is important to developing better high-energy lithium-ion batteries, such as those used in electric vehicles, because surface reactivity leads to material degradation.

At Lawrence Berkeley National Laboratory (Berkeley Lab), researchers found that a different way to make a cathode may mean better batteries. The cathode is the positive electrode in a battery, and development of an improved cathode material is considered essential to achieving a stable high-voltage cell, which has been the subject of intense research.

The researchers recently discovered that a simple and inexpensive technique, called spray pyrolysis, offers substantial improvements. Spray pyrolysis is a commercially available technique used for making thin films and powders but has not been widely used to make materials for battery production.

“We made some regular material using this technique, and lo and behold, it performed better than expected,” says Berkeley Lab battery scientist Marca Doeff. “We were at a loss to explain this, and none of our conventional material characterization techniques told us what was going on, so we went to SLAC (National Accelerator Laboratory) and Brookhaven (National Laboratory) to use more advanced imaging techniques and found that there was less nickel on the particle surfaces, which is what led to the improvement. High nickel content is associated with greater surface reactivity.”

Doeff says they are not the first ones to come up with the idea of decreasing nickel on the surface, but they were able to do it in one step using a very simple procedure. The results are significant because they have the potential to pave the way for making lithium-ion batteries that are cheaper and have higher energy density.

The research was supported by the Energy Department’s Vehicle Technologies Office and published online in the journal Nature Energy.

According to the Energy Department, a U.S. transition to light-duty hybrid electric (HEV) and plug-in electric (PEV) vehicles could reduce U.S. foreign oil dependence by 30-60 percent and greenhouse gas emissions by 30-45 percent, depending on the exact mix of technologies. Improving the batteries for electric drive vehicles, including HEV and PEV cars, is key to improving vehicles' economic, social, and environmental sustainability, says the Energy Department.


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