Berkeley Lab researchers discover way to increase battery energy density

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Researchers with Lawrence Berkeley National Laboratory have pinned down a poorly understood means of enhancing lithium-ion batteries, unlocking the power to boost performance in a multitude of common electronics.

The researchers deciphered the chemical mechanism of energy transfer in lithium-enriched batteries — which were suggested to be successful in previous research —  by revealing an unknown role of oxygen in the reaction. The findings were published in Nature Chemistry, according to a campus press release.

Gerbrand Ceder, the lead investigator of the study, said the findings could lead to the creation of batteries with higher energy density  — the amount of electricity generated for a given battery massincreasing energy efficiency in technology including electric vehicles and power grids.

“Energy storage is important for many of the things we do, whether it’s carrying our phone and not having to charge it to bigger societal issues,” Ceder said.

Lithium batteries are composed of two types of electrodes — an anode and a cathode — which energy-carrying lithium ions and electrons shuttle between to generate electrical current.  According to Ceder, lithium ions are stored in the anode when a device is charging and migrate to the cathode when the device is in usecausing energy to flow in a cycle similar to “pumping water up and letting it run down a waterfall again.”

Conventional batteries also employ transition metals, such as cobalt, to absorb and release electrons for energy transfer, according to Alexander Urban, a co-author of the study. He noted that transition metals were expensive and heavy, reducing the net energy density of a battery.

According to Ceder, however, the study demonstrated that scientists could leverage oxygen —  previously thought to glue other electrode compounds together without reacting — to release electrons under certain conditions instead.

Urban remarked that before lithium-excess batteries become commercialized, scientists would have to understand the stability of new electrode material to avoid risks such as explosions.

According to Katherine Harry, a campus graduate student researching lithium batteries, “the elephant in the room is that you need to (store battery energy) safely … in as small of a space and mass as possible.”  She added that extracting energy reproducibly “every time, thousands of times” posed another challenge to designing optimized batteries.

Dong-Hwa Seo, a lead author of the study, said redesigning the oxygen composition of the cathode material could potentially improve the stability of the batteries.

Ceder also mentioned that solid state batteries, which don’t contain flammable liquid, could prove safer and longer-lasting alternatives to conventional batteries, while remaining compatible with ideas put forth in the recent study.

“We’re actually doing a pretty decent job if you look at trends in energy density per cost per time over the last twenty years,” Harry said.  “We’ve made some significant strides.”

Contact Kimberly Nielsen at [email protected].