Revitalizing batteries by bringing 'dead' lithium back to life
Islands of inactive lithium creep like worms to reconnect with their electrodes, restoring a battery's capacity and lifespan

Date:
January 4, 2022
Source:
DOE/SLAC National Accelerator Laboratory
Summary:
Scientists brought islands of "dead" lithium back to life by making
them creep worms to reconnect with their electrodes in next-gen
lithium metal batteries. This extended battery life by nearly 30%.



FULL STORY ========================================================================== Researchers at the Department of Energy's SLAC National Accelerator
Laboratory and Stanford University may have found a way to revitalize rechargeable lithium batteries, potentially boosting the range of electric vehicles and battery life in next-gen electronic devices.


==========================================================================
As lithium batteries cycle, they accumulate little islands of inactive
lithium that are cut off from the electrodes, decreasing the battery's
capacity to store charge. But the research team discovered that they could
make this "dead" lithium creep like a worm toward one of the electrodes
until it reconnects, partially reversing the unwanted process.

Adding this extra step slowed the degradation of their test battery and increased its lifetime by nearly 30%.

"We are now exploring the potential recovery of lost capacity in
lithium-ion batteries using an extremely fast discharging step," said
Stanford postdoctoral fellow Fang Liu, the lead author of a study
published Dec. 22 in Nature.

Lost connection A great deal of research is looking for ways to make rechargeable batteries with lighter weight, longer lifetimes, improved
safety, and faster charging speeds than the lithium-ion technology
currently used in cellphones, laptops and electric vehicles. A particular
focus is on developing lithium-metal batteries, which could store more
energy per volume or weight. For example, in electric cars, these next-generation batteries could increase the mileage per charge and
possibly take up less trunk space.



==========================================================================
Both battery types use positively charged lithium ions that shuttle back
and forth between the electrodes. Over time, some of the metallic lithium becomes electrochemically inactive, forming isolated islands of lithium
that no longer connect with the electrodes. This results in a loss of
capacity and is a particular problem for lithium-metal technology and
for the fast charging of lithium-ion batteries.

However, in the new study, the researchers demonstrated that they could mobilize and recover the isolated lithium to extend battery life.

"I always thought of isolated lithium as bad, since it causes batteries
to decay and even catch on fire," said Yi Cui, a professor at Stanford
and SLAC and investigator with the Stanford Institute for Materials and
Energy Research (SIMES) who led the research. "But we have discovered how
to electrically reconnect this 'dead' lithium with the negative electrode
to reactivate it." Creeping, not dead The idea for the study was born
when Cui speculated that applying a voltage to a battery's cathode and
anode could make an isolated island of lithium physically move between the electrodes -- a process his team has now confirmed with their experiments.



==========================================================================
The scientists fabricated an optical cell with a lithium-nickel-manganese- cobalt-oxide (NMC) cathode, a lithium anode and an isolated lithium
island in between. This test device allowed them to track in real time
what happens inside a battery when in use.

They discovered that the isolated lithium island wasn't "dead" at all
but responded to battery operations. When charging the cell, the island
slowly moved towards the cathode; when discharging, it crept in the
opposite direction.

"It's like a very slow worm that inches its head forward and pulls
its tail in to move nanometer by nanometer," Cui said. "In this case,
it transports by dissolving away on one end and depositing material
to the other end. If we can keep the lithium worm moving, it will
eventually touch the anode and reestablish the electrical connection."
Boosting lifetime The results, which the scientists validated with other
test batteries and through computer simulations, also demonstrate how
isolated lithium could be recovered in a real battery by modifying the
charging protocol.

"We found that we can move the detached lithium toward the anode during discharging, and these motions are faster under higher currents," said
Liu. "So we added a fast, high-current discharging step right after the
battery charges, which moved the isolated lithium far enough to reconnect
it with the anode.

This reactivates the lithium so it can participate in the life of the
battery." She added, "Our findings also have wide implications for the
design and development of more robust lithium-metal batteries." This work
was funded by the DOE Office of Energy Efficiency and Renewable Energy,
Office of Vehicle Technologies under the Battery Materials Research
(BMR), Battery 500 Consortium and eXtreme Fast Charge Cell Evaluation
of Li-ion batteries (XCEL) programs.

========================================================================== Story Source: Materials provided by
DOE/SLAC_National_Accelerator_Laboratory. Original written by Jennifer
Huber. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Fang Liu, Rong Xu, Yecun Wu, David Thomas Boyle, Ankun Yang,
Jinwei Xu,
Yangying Zhu, Yusheng Ye, Zhiao Yu, Zewen Zhang, Xin Xiao, Wenxiao
Huang, Hansen Wang, Hao Chen, Yi Cui. Dynamic spatial progression
of isolated lithium during battery operations. Nature, 2021; 600
(7890): 659 DOI: 10.1038/s41586-021-04168-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220104095611.htm
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