High-capacity battery anode material offers graphite alternative

Skoltech researchers have investigated the use of polyaromatic hydrocarbons as anode materials in metal-ion batteries. The high capacity, low operating voltage, and high electronic conductivity of carbon-based compounds make them a promising anode material.

The results of the study, published in the Journal of Energy Storage, open up prospects for creating cheaper and even more capacious anode materials.

Metal-ion batteries use graphite as their main anode material today. There are several drawbacks to it, such as its small capacity, which restricts the operating time of phones, computers, and other equipment, and its high cost. To produce it, the raw material must be burned at a temperature of about 3,000 degrees Celsius.

“Over the past few years, scientists have been actively looking toward creating anodes from organic materials such as polyaromatic hydrocarbons,” said Senior Research Scientist Ilya Chepkasov from the Skoltech Energy Transition Center, the lead author of the study.

“They are cheaper and even more capacious than graphite. In our new work, we took four polyaromatic hydrocarbons—naphthalene, anthracene, tetracene, and pentacene—and intercalated various atoms—lithium, sodium, calcium, magnesium, rubidium, and potassium. All these metals are used in metal-ion batteries.”

Polyaromatic hydrocarbons result from low-temperature combustion or thermal decomposition of organic materials. The main focus of the work is on the intercalation of atoms of alkali and alkaline earth metals (lithium, sodium, potassium, rubidium, magnesium, calcium) into the crystal structures of polyaromatic compounds. The calculations were done based on density functional theory.

The team examined different approaches to rectify Van der Waals interactions that affect the accuracy of calculations on the energy of metal intercalation into polyaromatic hydrocarbon crystals.

“We concluded that the capacity of all the studied crystals of polyaromatic hydrocarbons with metals significantly exceeds the standard values for a graphite electrode. For example, the capacity of lithium, sodium, potassium, and rubidium is 1.2–1.3 times higher than that of graphite. And with the intercalation of magnesium and calcium, this value reaches even higher values—about 2.3–2.6 times higher,” said study co-author Professor Alexander Kvashnin from the Skoltech Energy Transition Center.

Polyaromatic hydrocarbons can enhance energy consumption in batteries, decrease the need for scarce elements (such as lithium), lessen the volumetric deformation of electrodes, and guarantee a quick charge-discharge reaction.

Tetracene and pentacene are particularly promising as anode materials. They open the way to creating more efficient and cost-effective solutions for storing electrical energy.