Page 276 - Polymer-based Nanocomposites for Energy and Environmental Applications

248 Polymer-based Nanocomposites for Energy and Environmental Applications

should be selected in conjunction with the electrolyte [88]. In the literature, two most
widely used ways to improve the most important properties of the cathode materials,
ionic conductivity and the electronic conductivity, are the carbon coating and the cat-
ion doping [106]. Carbon coating is a cheap and feasible strategy to improve the elec-
tronic conductivity of the cathode materials. In this technique, high-conductivity
carbon materials such as CNTs or graphene are coated on the cathode materials
and have shown to improve the electronic conductivity by long way [107].
The use of nanotechnology in the nanostructured cathode material synthesis and
characterization has played an important role. It is known that the nanoscale materials
show set of extraordinary properties in comparison with the macrosize materials. The
remarkable shape- and size-related nanomaterials can prove to be great tools for the
improvement in the properties of the electrodes [108–111]. The nanostructured cath-
ode materials show better energy storage capacity, improved charge-discharge kinet-
ics, and better cyclic stability due to the large surface area for assisting the faradic
reactions and shorter distance for the ions and electron transfer and freedom for vol-
ume changes during the intercalation/deintercalation process [112]. Nanostructured
lithium transition metal oxides such as LiNi 0.5 Mn 1.5 O 4 [113], layered oxides such
as V 2 O 5 in the nanobelts [114], nanostrips [115], and nanostructured MnO 2 [116].
Several excellent reviews have been published recently on the nanostructured cathode
materials [90,117,118].
Polymer nanocomposites made from conducting polymers with an inorganic
nanofiller have been used as cathode materials for the Li-ion batteries either as
stand-alone material or as a polymer nanocomposite. Conducting polymers are a class
of organic polymer that possess electric conductivity at ambient temperature and may
show behavior similar to the metal or semiconductors [21,28,119]. Conducting poly-
mers show excellent tailorability, low cost, flexibility, and processibility, and their
properties can be tailored by choosing appropriate synthesis procedure [120]. Their
synthesis and raw material are also very easy and abundant. Most popular conducting
materials are polyaniline (PANI) [26], polypyrrole (PYy) [121], and polythiophene
(PT) [122]. Polyaniline has been explored as cathode material for Li-ion batteries,
but they used alone show instability and low ionic conductivity for Li ions [22].
For this reason, polymer nanocomposites have been explored as cathode material
for Li-ion batteries because it shows remarkable properties due to the synergic inter-
action between the conducting polymer and inorganic filler [15]. The inorganic fillers
possess high Li-ion transport conductivity, good crystallinity, excellent electric con-
ductivity, and good redox properties [123]. The conducting polymer with embedded
nanoparticles shows good structural diversity, flexibility, durability, high porosity,
and good electric conductivity. The polymer acts as buffer for the anode in which vol-
ume changes occur during the intercalation and deintercalation process and high ionic
conductivity due to shorter diffusion path because of nanomaterials [124]. Several
polymer nanocomposite materials have been explored as cathode materials. For exam-
ple, vanadium oxide is a popular intercalation compound that can be used as cathode
for Li batteries owing to its layered structure, low cost, high theoretical capacity
1
(440 mAh g ), ease of synthesis, and abundance and better safety [112,114,125].
However, in practice, there are several challenges such as low ionic and electronic