10 kilograms
of petroleum is enough for a conventional car to travel 100 kilometers and
longer. But for the same distance, an electric car would need more than 100
kilograms of lithium ion batteries. The distance of electric vehicles is limited
by the insufficient energy density of the battery – the amount of energy that one
kilogram of battery can store and release. After years of development, the
energy density of lithium ion batteries is approaching its theoretical operation limit.
A leap forward in energy density would require a brand new type of battery.
This is why lithium metal batteries are garnering so much more attention nowadays. By
using lithium metal, which is a pure substance, instead of the graphite anode used in
lithium-ion batteries, the theoretical energy density of a lithium metal
battery can be several times higher than that of conventional lithium ion
batteries.
However,
this technology has a major concern: safety. During the charging and
discharging processes of the lithium metal battery, an unwanted structure, called
the lithium dendrite, may form on the surface of the electrode. Lithium
dendrite can decrease the energy density of the battery, and in the worst
case, cause short circuits in the battery, which can lead to overheating,
fire, or even explosion. This is the problem that has hindered the development
of lithium metal batteries for many years.
Yingying Lu
has been dedicated to energy-related fundamentals and safety problems in
batteries for years. By revealing the underlying mechanisms of the formation of
lithium dendrite, she found new ways
to undermine or even eliminate the dendrite problem. Lu demonstrated several
methods that can realize the stable electrodeposition of lithium along the
electrode surface. She has also successfully created a nearly dendrite-free deposition, and furthermore, has developed new electrolytes and electrodes, making the energy storage
capacity of lithium metal batteries several times higher than today’s
lithium ion batteries. High energy density and safety can be achieved simultaneously
for this promising energy carrier. “She
has single-handedly solved a problem widely regarded as a grand-challenge
problem in the batteries field,” said Prof. Lynden A. Archer, the National
Academy of Engineering in US, Professor of Cornell University, and Lu’s advisor
during her Ph.D. studies.
