ABSTRACT
Lithium-air (Li-air) batteries are regarded as a transformational
energy storage technology and categorized under advanced green
energy power sources for the future. In Li-air technology, oxygen
from ambient air is consumed at the cathode during discharge and
the pure oxygen (O2) is released during recharge of the battery.
In this advanced conversion technology, elemental lithium metal
and atmospheric oxygen form an electrochemical couple yielding
the highest theoretical energy density of 11,680 Whkg−1, the value very close to the energy released on combustion of liquid gasoline
(13,000 Whkg−1). Li-air battery system involves the reduction
of nonportable O2 via 2e − transfer process in aprotic medium,
while in aqueous medium, it exhibits either a 2e− or 4e− transfer. Accordingly, in aprotic medium, ORR (oxygen reduction reaction)
results in the formation of Li2O2 during charge and the OER
(oxygen evolution reaction) process promotes the decomposition
of Li2O2 during discharge. What is considered paramount in Li-air
system is the construction of an efficient gas diffusion electrode
(GDE) made of engineered nanoporous carbons (activated carbons,
carbon blacks, carbon monoliths, carbon foams, graphene, and so
on) embedded with bifunctional nanocatalysts (metal oxides for
instance) to felicitate both ORR andOER. This chapter presents great
challenges which exist at the cathode side (air) of Li-air system, the
importance of nano electro-catalysts, and how it helps achieve high
reversibility, high energy density, and round trip efficiency in Li-air
batteries.