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Nanolithia Cathode Battery: New Lithium-Oxygen Battery greatly improves Energy Efficiency, Longevity

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Lithium-air batteries are considered highly
promising technologies for electric cars and portable electronic devices because of their
potential for delivering a high energy output in proportion to their weight. But such batteries have some pretty serious
drawbacks: They waste much of the injected energy as heat and degrade relatively quickly. They also require expensive extra components
to pump oxygen gas in and out, in an open-cell configuration that is very different from
conventional sealed batteries. But a new variation of the battery chemistry,
which could be used in a conventional, fully sealed battery, promises similar theoretical
performance as lithium-air batteries, while overcoming all of these drawbacks. The new battery concept, called a nanolithia
cathode battery, is described in the journal Nature Energy. One of the shortcomings of lithium-air batteries,
is the mismatch between the voltages involved in charging and discharging the batteries. The batteries’ output voltage is around
1.2 volts lower than the voltage used to charge them, which represents a significant power
loss incurred in each charging cycle. 30 percent of the electrical energy is wasted
as heat in charging. Conventional lithium-air batteries draw in
oxygen from the outside air to drive a chemical reaction with the battery’s lithium during
the discharging cycle, and this oxygen is then released again to the atmosphere during
the reverse reaction in the charging cycle. In the new variant, the same kind of electrochemical
reactions take place between lithium and oxygen during charging and discharging, but they
take place without ever letting the oxygen revert to a gaseous form. Instead, the oxygen stays inside the solid
and transforms directly between its three redox states, while bound in the form of three
different solid chemical compounds, Li2O, Li2O2, and LiO2, which are mixed together
in the form of a glass. This reduces the voltage loss by a factor
of five, from 1.2 volts to 0.24 volts, so only 8 percent of the electrical energy is
turned to heat. This means faster charging for cars, as heat
removal from the battery pack is less of a safety concern, as well as energy efficiency
benefits. This approach helps overcome another issue
with lithium-air batteries: As the chemical reaction involved in charging and discharging
converts oxygen between gaseous and solid forms, the material goes through huge volume
changes that can disrupt electrical conduction paths in the structure, severely limiting
its lifetime. The secret to the new formulation is creating
minuscule particles, at the nanometer scale, which contain both the lithium and the oxygen
in the form of a glass, confined tightly within a matrix of cobalt oxide. The researchers refer to these particles as
nanolithia. In this form, the transitions between LiO2,
Li2O2, and Li2O can take place entirely inside the solid material. The nanolithia particles would normally be
very unstable, so the researchers embedded them within the cobalt oxide matrix, a sponge-like
material with pores just a few nanometers across. The matrix stabilizes the particles and also
acts as a catalyst for their transformations. Conventional lithium-air batteries are really
lithium-dry oxygen batteries, because they really can’t handle moisture or carbon dioxide,
so these have to be carefully scrubbed from the incoming air that feeds the batteries. We need large auxiliary systems to remove
the carbon dioxide and water, and it’s very hard to do this. But the new battery, which never needs to
draw in any outside air, circumvents this issue. The new battery is also inherently protected
from overcharging, because the chemical reaction in this case is naturally self-limiting — when
overcharged, the reaction shifts to a different form that prevents further activity. With a typical battery, if you overcharge
it, it can cause irreversible structural damage or even explode. In cycling tests, a lab version of the new
battery was put through 120 charging-discharging cycles, and showed less than a 2 percent loss
of capacity, indicating that such batteries could have a long useful lifetime. And because such batteries could be installed
and operated just like conventional solid lithium-ion batteries, without any of the
auxiliary components needed for a lithium-air battery, they could be easily adapted to existing
installations or conventional battery pack designs for cars, electronics, or even grid-scale
power storage. Because these “solid oxygen” cathodes
are much lighter than conventional lithium-ion battery cathodes, the new design could store
as much as double the amount of energy for a given cathode weigh. All of this is accomplished without adding
any expensive components or materials. The team expects to move from this lab-scale
proof of concept to a practical prototype within about a year.

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2 thoughts on “Nanolithia Cathode Battery: New Lithium-Oxygen Battery greatly improves Energy Efficiency, Longevity”

  1. Rodrigo Garduño says:

    Amazing!

  2. Steffen Frost says:

    Why did they stop at 120 cycles. What is data for 120+ cycles, like 500 cycles, 1000 cycles, 10,000 cycles. Also, what is the performance with respect to temperature. Will this work at -50C and +50C?

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