Tech Briefs Magazine - February 2022 - BT-19

High-Performance MXene Electrodes for NextGeneration
Battery
Two-dimensional MXene provides fast redox and high-rate energy storage.
City University of Hong Kong, Kowloon
wo-dimensional MXene has become
popular in the energy world because
of its fast energy storage capability.
But unstable voltage output limits applications.
A research team developed battery-like
electrochemical Nb2CTx MXene
electrodes with stable voltage output
and high energy density using a highvoltage
scanning strategy.
MXene is a large family of two-dimensional
nanomaterials and has been the
research focus of 2D materials in the
energy storage field in the past decade.
Because of excellent electronic conductivity
and large surface area, MXene features
fast surficial redox and demonstrates
high-rate energy storage.
But the biggest challenge of MXene
energy storage is that all reported
MXene electrodes lack a distinct discharge
voltage plateau, which means
they discharge with a rapidly descending
output voltage. This shortcoming deteriorates
Mxene's energy density and the
stable energy output at desired high
voltage regions, leading to limited energy
density, usually less than 100 Wh kg-1.
To overcome the problem of unstable
energy output, the research team developed
battery-type Nb2CTx MXene elecT
Battery-like
electrochemical MXene electrodes are the black substance inside the bottle. The
silver " buttons " next to the bottle are batteries; in the background is the battery testing system.
(Photo: City University of Hong Kong)
trodes. The team revealed completely different
electrochemical properties of the
Nb2CTx MXene electrode by regulating
the voltage windows from 2.0 V to 2.4 V.
Under high-voltage scanning up to 2.4 V,
the Nb2CTx MXene electrode showed typical
battery-type features different from
the one under low voltage and other previously
reported MXene systems.
The team discovered that the Nb2CTx/
Zn battery could exhibit superior rate
capability, durable cyclic performance,
and high energy density under high-voltage
scanning. More importantly, they succeeded
in equipping MXene with a flat
and stable discharge plateau of 1.55 V to
boost energy densities. A high-level
energy density among all aqueous
Mxene electrodes of 146.7 Wh kg-1 with
63 percent contribution from the plateau
region was also obtained.
      
    
   
Technique Merges Solar Cell and Liquid Battery
A highly efficient and long-lasting solar flow battery generates, stores, and redelivers renewable electricity
from the Sun in one device.
 University of Wisconsin, Madison, WI
A
solar flow battery was developed that
is made of silicon solar cells combined
with advanced solar materials
integrated with optimally designed chemical
components. While solar flow batteries
are years away from commercialization,
they offer the potential to provide reliable
electricity generation and storage for lighting,
cellphones, or other fundamental uses
for homes in remote areas. They combine
Battery & Electrification Technology, February 2022
the advantages of photovoltaic cells that
convert sunlight into electricity with the
advantages of flow batteries, which use
tanks of chemicals that can react to produce
electricity and be recharged by the
solar cells.
Since the Sun doesn't always shine, storage
is key for practical solar electricity,
especially in remote and rural regions with
a lot of sunlight such as in the sunbelt
regions of the US, Australia, Saudi Arabia,
and Africa. Many solar home systems use
lead-acid or lithium-ion batteries for electricity
storage. Flow batteries could be less
expensive at a larger scale and are an ideal
storage choice for merging with solar cells.
The researchers turned to an increasingly
popular material for photovoltaic cells:
halide perovskites. The solar conversion
efficiency of these special materials has
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Tech Briefs Magazine - February 2022

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