Environmental Engineering Reference
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at the cathode:
NiCl 2 þ 2Na þ þ 2e ! Ni þ 2NaCl
ð 5 : 19 Þ
to have the following overall cell reaction:
2Na + NiCl 2 ! 2NaCl + Ni
ð 5 : 20 Þ
with a cell potential of 2.58 V at the working temperature. During discharge the
sodium ions produced at the anode are transported through the electrolyte to the
cathode, where react with NiCl 2 to form NaCl. During charge sodium metal and
nickel chloride are re-generated. The specific energy is about 100 Wh/kg with a
specific power of 150 W/kg.
Generally, the heat insulation is guaranteed by a double skinned stainless steel
box with 2-3 cm insulation layer between the skins. Moreover the insulation is
completely empty of all gas and it works in vacuum condition.
In order to keep the Zebra batteries at the high temperature required for their
operation, they need to be kept connected to the electric network when they are not in
use. This represents a limitation of their application, and makes them more suitable
specifically for public transportation means, rather than small private vehicles.
Limitations in the production and commercial development of these batteries are
essentially due to the fact that they will never be used for laptop and mobile phones.
5.3.2.6 Lithium Batteries
Lithium batteries are showing a great potential to provide electric vehicles with
sufficient performance in terms of acceleration and driving range [ 5 ]. Lithium
metal is attractive as battery anode material mainly due to its lightness and high
voltage. The use of a lithium based anode in these systems implies some concerns
of safety hazard, due to the high reactivity of the metal. For this reason, in the so-
called lithium-ion batteries, both positive and negative electrodes employ lithium
''host'' compounds, where an intercalation process occurs, i.e., lithium ions are
reversibly removed or inserted without a significant structural change to the host.
The negative material is based on graphitic carbon, while the positive one is
realized by using a metal oxide as lithium source compound, of the LiMO 2 or
LiMO 4 type (M = Co, Ni, or Mn). In these systems the lithium ion conducting
electrolyte is based on a solution of a lithium salt in organic solvents [ 20 ]. The
resulting electrochemical reaction is the following:
ð 5 : 21 Þ
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