Record-breaking lithium-metal cell
Nickel-rich cathode and ionic liquid electrolyte enable extremely high
energy density and good stability

Date:
August 24, 2021
Source:
Karlsruher Institut fu"r Technologie (KIT)
Summary:
A new type of lithium-metal battery reaches an extremely high energy
density of 560 watt-hours per kilogram -- based on the total weight
of the active materials -- with a remarkable stability. Researchers
used a promising combination of cathode and electrolyte: The
nickel-rich cathode enables storage of high energy per mass,
the ionic liquid electrolyte ensures largely stable capacity over
many cycles.



FULL STORY ==========================================================================
A new type of lithium-metal battery reaches an extremely high energy
density of 560 watt-hours per kilogram -- based on the total weight of
the active materials -- with a remarkable stability. Researchers used a promising combination of cathode and electrolyte: The nickel-rich cathode enables storage of high energy per mass, the ionic liquid electrolyte
ensures largely stable capacity over many cycles.


========================================================================== Currently, lithium-ion batteries represent the most common solution
for mobile power supply. In some applications, however, this
technology reaches its limits. This especially holds for electric
mobility, where lightweight and compact vehicles with large ranges
are desired. Lithium-metal batteries may be an alternative. They are characterized by a high energy density, meaning that they store much
energy per mass or volume. Still, stability is a problem, because the
electrode materials react with conventional electrolyte systems.

Researchers of Karlsruhe Institute of Technology (KIT) and the Helmholtz Institute Ulm for Electrochemical Energy Storage (HIU) have now found a solution. As reported in Joule, they use a promising new combination
of materials. A cobalt-poor, nickel-rich layered cathode (NCM88)
reaches a high energy density. With the usually applied, commercially
available organic electrolyte (LP30), however, stability leaves a lot
to be desired. Storage capacity decreases with an increasing number
of cycles. Professor Stefano Passerini, Director of HIU and Head of
the Electrochemistry for Batteries Group, explains the reason: "In the electrolyte LP30, particles crack on the cathode. Inside these cracks,
the electrolyte reacts and damages the structure.

In addition, a thick mossy lithium-containing layer forms on
the anode." For this reason, the scientists used a non-volatile, poorly-flammable, dual-anion ionic liquid electrolyte (ILE) instead. "With
the help of ILE, structural modifications on the nickel-rich cathode can
be reduced significantly," says Dr. Guk-Tae Kim from the Electrochemistry
for Batteries Group of HIU.

Capacity Keeps 88 Percent after 1000 Cycles The results: The lithium-metal battery with the NCM88 cathode and the ILE electrolyte reaches an energy density of 560 watt-hours per kilogram (Wh/kg) - - based on the total
weight of the active materials. Its initial storage capacity is 214
milliampere hours per gram (mAh g-1) of the cathode material.

After 1000 cycles, 88 percent of the capacity are retained. The average Coulombic efficiency, i.e., the ratio between discharge and charge
capacity, is 99.94 percent. As the battery is characterized by a high
safety, the researchers have made an important step towards carbon-neutral mobility.

========================================================================== Story Source: Materials provided by
Karlsruher_Institut_fu"r_Technologie_(KIT). Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Fanglin Wu, Shan Fang, Matthias Kuenzel, Angelo Mullaliu,
Jae-Kwang Kim,
Xinpei Gao, Thomas Diemant, Guk-Tae Kim, Stefano
Passerini. Dual-anion ionic liquid electrolyte enables stable
Ni-rich cathodes in lithium-metal batteries. Joule, 2021; 5 (8):
2177 DOI: 10.1016/j.joule.2021.06.014 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210824135339.htm

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