Battery Technology Overview Today
Battery Power
1.1.1 Introduction
All spacecraft that orbit the Earth
need batteries during the eclipse periods, peak load periods, and during the
initial launch operations. In the 1980’s the Hubble Telescope chose Lead-Acid
batteries because of their reliability
and due to the fact other newer batteries technologies have not matured such as
the Lithium, and Nickel Cadmium batteries that are used today in aircraft and
spaceflight. There are a wide variety
of batteries used in space flight as shown below.
The primary power supply batteries
are considered not rechargeable, whereas the secondary battery is used to store
energy such as Ni-Cd, and nickel-hydrogen batteries that have been used on the
Galileo spacecraft [1]
1.1.2 Ni-Cd Battery
There are four main components of a Nickel-Cadmium (NiCd) cell:
·
Negative
plate made of cadmium
·
The
positive plates – Is composed of nickel which accepts electrons from returning
external loads.
·
The
electrolyte – An aqueous potassium hydroxide solution which completes the
internal circuit.
·
Fibrous
plastic fabric separator – It holds the electrolyte in place, and isolates the
positive and negative plates.
The batteries are hermetically
sealed, but they must not be overcharged due to the release of hydrogen gas.
The voltage is 1.1 V discharged, and 1.4 V fully charged. A typical cell
battery has an average discharge voltage of
Vave is 27.5 V. The cycle time is approximately 6000 cycles
per year. When used in a geosynchronous spacecraft the battery is only 100 cycles
per year.
Batteries are considered the most
temperature-sensitive elements of the spacecraft. Low temperatures will reduce
the rate of oxygen recombination in the cell and can result in the incomplete
recharging and cause high cell pressure.
1.1.3 Ni-H2 Battery
The introduction of NiH2
is replacing Ni-Cd batteries as the dominant batteries used on spacecraft due
to their reliability. The nickel electrode is the same as in the NiCd battery,
except for the opposing hydrogen electrode which is akin to the fuel cell
electrocatalytic diffusion electrode. The battery uses hydrogen gas as the
anodic active material.
When charges nickel is oxidized, and
hydrogen gas is evolved at the hydrogen electrode. Nickel-hydrogen offer improved mass, cycle life, and reduced
failure when compared to NiCd batteries.
1.1.4 Ni-MH Battery
Nickel Metal hydride (NiMH) batteries
have a higher storage capacity than other batteries including lead acid. They
can store more energy in less space, and contain less toxic chemical than
lithium ion and lead acid batteries. Their extensive use in home electronics
products has proven their safety and use in the private sector.[2]
1.1.5 Ni-Zn Battery (ultra-high power density)
The Ni-Zn is considered the next-generation of batteries
to be used for fuels cells and space applications. They are highly-reliable,
small, and light weight as practical applications for medical devices, due to
their long-life, low-cost as rechargeable batteries for space and defense
applications.[3]
1.1.6 Li-Ion Battery
Lithium-ion batteries have a higher
energy density than lead acid and NiMh. The drawback is that they have toxic
disposal problems with the lithium. They are more expensive to manufacture than
NiMh batteries. They are the mainstay of battery being used today!
1.1.7 Li-Carbon Battery and carbon nanotubes
Lithium-carbon batteries have
promising due to their high density with the ability to produce 100 Wh/kg at
battery level. Lithium is used as the negative electrode and layered-structure
carbon electrode. The design of the
cells will allow oxygen to recombine chemically at the negative electrodes.
This will prevent excessive buildup of pressure in a sealed cell. This is very
appealing compared to other batteries that have the risk of excessive gas
buildup when overcharged. [4]
There are promising uses of carbon
nanotube electrodes in the use of electronics to electric vehicles with their
superior energy density, lighter, thinner, and high capacity. The use of carbon
nanotubes (CNT’s) are excellent materials for lithium ion batteries due to the
ultra-high capacity anode materials anode materials. Lithium ion capacities for
CNT-based anodes can exceed 1000 mAh g-1. [5]
1.1.8 Mg-Air Battery (ultra-high energy density)
Magnesium-Air system is in the class of metal-air batteries.
They are important sources for electronics and vehicle due to their high
theoretical energy density and low cost. Recent progress in Mg or MG alloys as
anode materials and typical classes of air cathode catalysts for Mg-air
batteries. The development of rechargeable Mg-air batteries, bi-functional
catalyst with reversible oxygen reduction and evolutions reactions makes this
class of battery and high level candidate for long deep space flight energy
storage systems.
The
circuit potential of the “oxygen shuttle” type battery for Mg-air oxide
batteries when using a Ca-stabilized ZrO2 electrode has an observed
circuit potential capacity was 1.81V and 1154 mA h gmg -1
1.1.9 Ultra-Capacitors
Super capacitors (SC) are electric double-layer capacitor
(EDLC) utilize the Helmholtz double layer at the battery interface to store
electrostatic charge. The separation of a conductor electrode and electrolytic
solution electrode are only a few Angstroms. Carbon electrodes achieve a higher
static double-layer capacitance than traditional pseudo-capacitors that utilize
metal oxide and conducting polymers. Maxwell Technologies are companies that
produce ultra-capacitors. The development
of nano structured batteries can store over a hundred times the amount of
charge than those with the same size and configurations.[8]
The application of enhanced carbon
nanotube ultra-capacitors can greatly increase the potential for
high-power storage for kinetic-energy weapons, power supplies, and control
systems for spacecraft. CNTs/MnO2 nano-composite as electrodes will
enhance the capacitance by >400X over CNT electrodes.[9]
Future spacecraft will demand higher
energy density as power requirements for devices increase. It is evident in the
table below that ultra-capacitors have potential use in the enhancement of
DC-DC converters by their integration into power conversion design for
spacecraft and commercial usage. High powered, high propulsion spacecraft would
greatly benefit by the use of ultra-capacitors in their electrical sub-systems.[10]
1.2 Fuel Cell Power
1.2.1 Regenerative fuel cells
Fuel cells have been used since the early days of Apollo
and used on the Space Shuttle as a component for the electrical power system.
They convert chemical energy into electricity though a chemical reaction with
an oxidizing agent and oxygen. The oxygen produced augment the environmental
system and hydrogen burned as fuel for propulsion.
They are many reasons to utilize fuel
cells.
·
Efficient
at the ability to extract hydrogen for use in combustion
·
Production
of fuel cells more efficient, and cleaner
·
Lighter
than batteries per energy unit
·
Higher
energy densities than conventional batteries
·
Waste
product is pure water, for use by astronauts.
·
Storing hydrogen
in a solid state such as lithium nitride and lithium carbon.
·
Lithium nitride
absorbs large amounts of hydrogen under pressure.
1.2.2 Space Shuttle fuel cells
The three fuel cell power plants are
coupled to the reactant of (hydrogen and oxygen) in a distribution subsystem,
the heart rejection subsystem, the potable water storage subsystem, and the
power distribution subsystem. The cells contain electrolyte composed of
potassium hydroxide and water with the oxygen electrode (cathode) and a
hydrogen electrode (anode). The resultant oxygen and hydrogen are consumed
relative to the orbiter’s electrical power demand, are constantly being renewed
in the process.[12]
1.2.3 Nanotube fuel cells
There are a variety of fuel cells that utilize materials that include H2,
N2H4, NH3, CH3OH3,
coal gas, and hydrocarbons.
This includes the development of fuel
cells utilizing nanotube technology. Single-wall carbon nanotubes have over
twice the storage capacity of graphite electrodes. Open-end and closed-end
nanotubes are 1.1 nanometers in diameter and 10,000 nanometers in length. The
higher capacity of shorter nanotube is because lithium ion has a higher uptake
though open ends. Nanotubes have a potentially higher capacity to store charges
than graphite.[13]
The prospect of using carbon nanotube
membranes will enable cheaper and more efficient fuel cells. There is a 40
percent performance improvement, 25 percent durability improvement, and lower
manufacturing cost of production.[14]
1.2.4 (PEM) Proton Exchange Membrane
The development of PEMFC fuel cells utilizes NaBH2 solution
with oxidation from direct borohydride fuel as the hydrogen carrier with
hydrolysis from H2 PEMFC. Research with fuel cells has yielded PEM
fuel cells composed of materials from a variety of aromatic polymers,
Polysulfones, Polyphenylenes, Phenylene Sulfphides, Arylene Ether Ketones,
The chemical reaction below utilizes the standard hydrogen
electrode:
BH4- + 8 OH > BO2 -+
6 H2O + 8 e-
The cost is high currently at $800
per m2 but will decrease in time as manufacturing fabrication
methodologies is improved. The current density efficiency of fuel cells is 0.5
A/cm2 that operate for more than 20,000 hours. Cells with an active
area of greater than 1000 cm2 and 10 KW-stacks contain 20 cells. [15]
Commercially produced material for
PEM for fuel cell applications is Nafion, a sufonated fluropolymer.
The applications of polymer
electrolyte fuel cell materials have characteristics and bulk properties of
proton conductivity, gas separation, and mechanical properties. This diversity
of materials for applications promotes the use of fuel cell batteries in a
myriad of applications as illustrated below.
[1] (Power Sources: Fuel Cells, Solar Cells and
Batteries, 2003)
[2] (Moody, 2010)
[3] (Jha, 2012)
[4] (Verniolle & Dudley, 1997)
[5] (Landi, 2009)
[6] (Zhang,
Taoa, & Chen, 2013; Zhang, Taoa, & Chen, 2013)
[7] (Inoishi & Ju, 2013)
[8] (Ingram, 2013)
[9] (Enhanced Carbon Nanotube Ultracapacitors, 2014)
[10] (Grbovic, 2014)
[11] (Esposito & Conti, 2009)
[12] (Fuel Cell Use in the Space Shuttle, 2014)
[13] (Power Sources: Fuel Cells, Solar Cells and
Batteries, 2003)
[14] (Zheng, 2014)
[15] (Esposito & Conti, 2009)
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