Researchers at Texas A&M University have invented a technology that can prevent lithium batteries from heating and failing, today.tamu.edu reports. Their carbon nanotube design for the battery’s conductive plate enables the safe storage of a large quantity of lithium ions, thereby reducing the risk of fire. The researchers said that their new anode architecture will help lithium batteries charge faster than current commercially available batteries.
“We have designed the next generation of anodes for lithium batteries that are efficient at producing large and sustained currents needed to quickly charge devices,” said Juran Noh, a material sciences graduate student in Choongho Yu’s laboratory in the J. Mike Walker ’66 Department of Mechanical Engineering. “Also, this new architecture prevents lithium from accumulating outside the anode, which over time can cause unintended contact between the contents of the battery’s two compartments, which is one of the major causes of device explosions.”
Their results are published in the March issue of the journal Nano Letters.
When lithium batteries are in use, charged particles move between the battery’s two compartments. Electrons given up by lithium atoms move from one side of the battery to the other. Lithium ions travel the other direction. When charging the battery, lithium ions and electrons go back to their original compartments.
Hence, the property of the anode, or the electrical conductor that houses lithium ions within the battery, plays a decisive role in the battery’s properties. A commonly used anode material is graphite. In these anodes, lithium ions are inserted between layers of graphite. However, Noh said this design limits the amount of lithium ions that can be stored within the anode and requires more energy to pull the ions out of the graphite during charging.
These batteries also have a more insidious problem. Sometimes lithium ions do not evenly deposit on the anode. Instead, they accumulate on the anode’s surface in chunks, forming tree-like structures, called dendrites. Over time, the dendrites grow and eventually pierce through the material that separates the battery’s two compartments. This breach causes the battery to short circuit and can set the device ablaze. Growing dendrites also affect the battery’s performance by consuming lithium ions, rendering them unavailable for generating a current.
Noh said another anode design involves using pure lithium metal instead of graphite. Compared to graphite anodes, those with lithium metal have a much higher energy content per unit mass or energy density. But they too can fail in the same catastrophic way due to the formation of dendrites.
To address this problem, Noh and her teammates designed anodes using highly conductive, lightweight materials called carbon nanotubes. These carbon nanotube scaffolds contain spaces or pores for lithium ions to enter and deposit. However, these structures do not bind to lithium ions favorably.