Rechargeable Sodium-ion Battery - The Future of Battery Development

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RECHARGEABLE SODIUM-ION BATTERY
(Na-ion, The future of battery development)
Author-DESH DEEPAK YADAV
TABLE OF CONTENTS
CHAPTER NO. TITLE PAGE NO.
ABSTRACT iv
1. INTRODUCTION 5
2 LITERATURE 6
2.1 Rechargeable Battery Technology 6
2.1.1 Charging and discharging 7
2.1.2 Usage and Applications 9
2.2 Battery Technology 10
2.2.1 History of Battery 10
2.2.2 Categories and types of Battery 11
2.3 Categories and types of Rechargeable Batteries 12
2.4 Li-ion Rechargeable battery 13
2.5 Advantage and Limitation of Li-on Battery 15
3. THE RECHARGEABLE REVOLUTION 17
4. FUTURE OF BATTERY DEVELOPMENT 19
3.1 Na-ion Rechargeable Battery 18
5. SODIUM AS A SUBSTITUTE OF LITHIUM 22
6. CONCLUSION 23
8. REFERENCES 24

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ABSTRACT
Lithium-ion batteries are everywhere, powering phones, cars, and laptops, among
other things. However, lithium is a relatively rare element, found in some locations
in South America. That not only keeps the price of lithium-ion batteries high, but
also makes the supply chain vulnerable to political instabilities.
Sodium has a very similar chemistry to lithium, and as soon as lithium-ion batteries
came to market, researchers started looking to sodium as a substitute for lithium in
rechargeable batteries. Unlike lithium, the reserves of sodium are practically
unlimited. The highest hurdle for sodium to clear on its way to battery dominance
is the development of suitable electrodes.
If batteries can get better, cheaper and store more power safely, then electric cars
and solar- or wind- powered homes become more viable - even on cloudy days or
when the wind isn't blowing. These types of technological solutions will be one of
the more hopeful aspects to beat global warming

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CHAPTER
1. INTRODUCTION
Sodium-ion batteries offer an attractive alternative to Li-ion batteries not because they
outperform Li-ion batteries, but mainly because of lower costs due to the the nearly unlimited
supply of sodium. They are also an attractive alternative in part because unlike their sodium-
sulfur battery cousins they can be made in similar sizes to Li-ion batteries.
However, the commercial development of sodium-ion batteries has been hampered by the
materials used in the negative electrodes. These swell to as much as 400 to 500 percent their
original size, leading to mechanical damage and loss of electrical contact.
Now researchers at Kansas State University United States have developed a composite, paper-
like material made from two 2-dimensional materials—molybdenum disulfide and graphene
Nano sheets—that has been shown to overcome this shortcoming.
In research published in the journal ACS Nano (“MoS2/Graphene Composite Paper for Sodium-
Ion Battery Electrodes”), the 2-D composite material developed proved resistant to the
“alloying” reaction that electrode materials typically suffer when in contact with sodium.
The research also marks the first time that the flexible paper electrode was used in an anode for
sodium-ion battery that operates at room temperature.

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2. LITERATURE
2.1 Rechargeable Battery Technology
A rechargeable battery, storage battery, secondary cell, or accumulator is a type of
electrical which can be charged, discharged into a load, and recharged many times, while a non-
rechargeable or primary battery is supplied fully charged, and discarded once discharged. It is
composed of one or more electrochemical cells. The term "accumulator" is used as
it accumulates and stores energy through a reversible electrochemical reaction. Rechargeable
batteries are produced in many different shapes and sizes, ranging from button cells to megawatt
systems connected to stabilize an electrical distribution network. Several different combinations
of electrode materials and electrolytes are used, including lead–acid, nickel
cadmium (NiCd), nickel metal hydride (NiMH), lithium ion (Li-ion), and lithium ion
polymer (Li-ion polymer).
Rechargeable batteries initially cost more than disposable batteries, but have a much lower total
cost of ownership and environmental impact, as they can be recharged inexpensively many times
before they need replacing. Some rechargeable battery types are available in the same sizes and
voltages as disposable types, and can be used interchangeably with them.
The mobile world depends on lithium-ion batteries — today's ultimate rechargeable energy store.
Last year, consumers bought five billion Li-ion cells to supply power-hungry laptops, cameras,
mobile phones and electric cars. “It is the best battery technology anyone has ever seen,” says
George Crabtree, director of the US Joint Center for Energy Storage Research (JCESR), which
is based at the Argonne National Laboratory near Chicago, Illinois. But Crabtree wants to do
much, much better.
Modern Li-ion batteries hold more than twice as much energy by weight as the first commercial
versions sold by Sony in 1991 — and are ten times cheaper. But they are nearing their limit.
Most researchers think that improvements to Li-ion cells can squeeze in at most 30% more
energy by weight. That means that Li-ion cells will never give electric cars the 800-kilometre
range of a petrol tank, or supply power-hungry smartphones with many days of juice.

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2.1.1 Charging and Discharging
During charging, the positive active material is oxidized, producing electrons, and the negative
material is reduced, consuming electrons. These electrons constitute the current flow in the
external circuit. The electrolyte may serve as a simple buffer for internal ion flow between
the electrodes, as in lithium-ion and nickel-cadmium cells, or it may be an active participant in
the electrochemical reaction, as in lead–acid cells.
The energy used to charge rechargeable batteries usually comes from a charger using AC mains
electricity, although some are equipped to use a vehicle's 12-volt DC power outlet. Regardless,
to store energy in a secondary cell, it has to be connected to a DC voltage source. The negative
terminal of the cell has to be connected to the negative terminal of the voltage source and the
positive terminal of the voltage source with the positive terminal of the battery. Further, the
voltage output of the source must be higher than that of the battery, but not much higher: the
greater the difference between the power source and the battery's voltage capacity, the faster the
charging process, but also the greater the risk of overcharging and damaging the battery.
Chargers take from a few minutes to several hours to charge a battery. Slow "dumb" chargers
without voltage or temperature-sensing capabilities will charge at a low rate, typically taking 14
hours or more to reach a full charge. Rapid chargers can typically charge cells in two to five
hours, depending on the model, with the fastest taking as little as fifteen minutes. Fast chargers
must have multiple ways of detecting when a cell reaches full charge (change in terminal voltage,
temperature, etc.) to stop charging before harmful overcharging or overheating occurs. The
fastest chargers often incorporate cooling fans to keep the cells from overheating.
Battery charging and discharging rates are often discussed by referencing a "C" rate of current.
The C rate is that which would theoretically fully charge or discharge the battery in one hour.
For example, trickle charging might be performed at C/20 (or a "20 hour" rate), while typical
charging and discharging may occur at C/2 (two hours for full capacity). The available capacity
of electrochemical cells varies depending on the discharge rate. Some energy is lost in the
internal resistance of cell components (plates, electrolyte, interconnections), and the rate of
discharge is limited by the speed at which chemicals in the cell can move about. For lead-acid
cells, the relationship between time and discharge rate is described by Peukert's law; a lead-acid
cell that can no longer sustain a usable terminal voltage at a high current may still have usable
capacity, if discharged at a much lower rate. Data sheets for rechargeable cells often list the

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Discharge capacity on 8-hour or 20-hour or other stated time; cells for uninterruptible systems
may be rated at 15 minute discharge.
Battery manufacturers' technical notes often refer to voltage per cell (VPC) for the individual
cells that make up the battery. For example, to charge a 12 V lead-acid battery (containing 6
cells of 2 V each) at 2.3 VPC requires a voltage of 13.8 V across the battery's terminals.
Non-rechargeable alkaline and zinc–carbon cells output 1.5V when new, but this voltage drops
with use. Most NiMH AA and AAA cells are rated at 1.2 V, but have a flatter discharge curve
than alkaline and can usually be used in equipment designed to use alkaline batteries
Source:https://www.google.co.in/imghp?hl=en&tab=wi&ei=8UZwVsjBM4OxuQTJj4zIBQ&ved=0EKouCBIo

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2.1.2 Usage and Applications
Rechargeable batteries are used for automobile starters, portable consumer devices, light
vehicles (such as motorized wheelchairs, golf carts, electric bicycles, and electric forklifts), tools,
and uninterruptible power supplies. Emerging applications in hybrid internal combustion-
battery and electric vehicles are driving the technology to reduce cost, weight, and size, and
increase lifetime.
Older rechargeable batteries self-discharge relatively rapidly, and have to be charged before first
use; some newer low self-discharge NiMH batteries hold their charge for many months, and are
typically sold factory-charged to about 70% of their rated capacity.
Grid energy storage applications use rechargeable batteries for load-leveling, storing electric
energy at times of low demand for use during peak periods, and for renewable energy uses, such
as storing power generated from photovoltaic arrays during the day to be used at night. Load-
leveling reduces the maximum power which a plant must be able to generate, reducing capital
cost and the need for peaking power plants.
The US National Electrical Manufacturers Association estimated in 2006 that US demand for
rechargeable batteries was growing twice as fast as demand for disposables.
Small rechargeable batteries are used to power portable electronic devices, power tools,
appliances, and so on. Heavy-duty batteries are used to power electric vehicles, ranging
from scooters to locomotives and ships. They are used in distributed electricity
generation and stand-alone power systems.
Source:https://www.google.co.in/imghp?hl=en&tab=wi&ei=8UZwVsjBM4OxuQTJj4zIBQ&ved=0EKouCBIoAQ

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2.2 Battery Technologies
An electric battery is a device consisting of two or more electrochemical cells that convert stored
chemical energy into electrical energy. Each cell has a positive terminal, or cathode, and a
negative terminal, or anode. The terminal marked positive is at a higher electrical potential
energy than is the terminal marked negative. The terminal marked positive is the source of
electrons that when connected to an external circuit will flow and deliver energy to an external
device. When a battery is connected to an external circuit, electrolytes are able to move as ions
within, allowing the chemical reactions to be completed at the separate terminals and so deliver
energy to the external circuit. It is the movement of those ions within the battery which allows
current to flow out of the battery to perform work. Although the term battery technically means
a device with multiple cells, single cells are also popularly called batteries.
2.2.1 History of Battery
In 1749 Benjamin Franklin, the U.S. polymath and founding father, first used the term "battery"
to describe a set of linked capacitors he used for his experiments with electricity. These
capacitors were panels of glass coated with metal on each surface.[1]
These capacitors were
charged with a static generator and discharged by touching metal to their electrode. Linking them
together in a "battery" gave a stronger discharge. Originally having the generic meaning of "a
group of two or more similar objects functioning together", as in an artillery battery, the term
came to be used for piles and similar devices in which many electrochemical cells were
connected together in the manner of Franklin's capacitors. Today even a single electrochemical
cell, e.g. a dry cell, is commonly called a battery.
Batteries provided the main source of electricity before the development of electric
generators and electrical grids around the end of the 19th century. Successive improvements in
battery technology facilitated major electrical advances, from early scientific studies to the rise
of telegraphs and telephones, and eventually leading to portable, mobile phones, electric cars,
and many other electrical devices.
Scientists and engineers developed several commercially important types of battery. "Wet
cells" were open containers that held liquid electrolyte and metallic electrodes. When the
electrodes were completely consumed, the wet cell was renewed by replacing the electrodes
and electrolyte. Open containers are unsuitable for mobile or portable use. Early electric cars
used semi-sealed wet cells.

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2.2.1 Categories and Types of Batteries
Batteries are classified into primary and secondary forms.
 Primary batteries irreversibly transform chemical energy to electrical energy. When the
supply of reactants is exhausted, energy cannot be readily restored to the battery.
 Secondary batteries can be recharged; that is, they can have their chemical reactions
reversed by supplying electrical energy to the cell, approximately restoring their
original composition.
Primary batteries, or primary cells, can produce current immediately on assembly. These are
most commonly used in portable devices that have low current drain, are used only
intermittently, or are used well away from an alternative power source, such as in alarm and
communication circuits where other electric power is only intermittently available. Disposable
primary cells cannot be reliably recharged, since the chemical reactions are not easily
reversible and active materials may not return to their original forms. Battery manufacturers
recommend against attempting to recharge primary cells.
In general, these have higher energy densities than rechargeable batteries,[23]
but disposable
batteries do not fare well under high-drain applications with loads under 75 ohms (75 Ω).
Common types of disposable batteries include zinc–carbon batteries and alkaline batteries.
Secondary batteries, also known as secondary cells, or rechargeable batteries, must be charged
before first use; they are usually assembled with active materials in the discharged state.
Rechargeable batteries are (re)charged by applying electric current, which reverses the chemical
reactions that occur during discharge/use. Devices to supply the appropriate current are called
chargers.
The oldest form of rechargeable battery is the lead–acid battery. This technology contains liquid
electrolyte in an unsealed container, requiring that the battery be kept upright and the area be
well ventilated to ensure safe dispersal of the hydrogen gas it produces during overcharging. The
lead–acid battery is relatively heavy for the amount of electrical energy it can supply. Its low
manufacturing cost and its high surge current levels make it common where its capacity (over
approximately 10 Ah) is more important than weight and handling issues. A common application
is the modern car battery, which can, in general, deliver a peak current of 450 amperes.

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2.3 COMPARISION OF RECHARGABLE BATTERIES
Source: https://en.wikipedia.org/wiki/Rechargeable_battery#Types
Source:
https://en.wikipedia.org/wiki/Rechargeable_battery#Types

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2.4 Li-ion Rechargeable Battery
Pioneer work with the lithium battery began in 1912 under G.N. Lewis but it was not until the
early 1970s that the first non-rechargeable lithium batteries became commercially available.
Lithium is the lightest of all metals, has the greatest electrochemical potential and provides the
largest energy density per weight.
Attempts to develop rechargeable lithium batteries followed in the 1980s, but failed due to safety
problems. Because of the inherent instability of lithium metal, especially during charging,
research shifted to a non-metallic lithium battery using lithium ions. Although slightly lower in
energy density than lithium metal, the Li-ion is safe, provided certain precautions are met when
charging and discharging. In 1991, the Sony Corporation commercialized the first Li-ion battery.
Other manufacturers followed suit. Today, the Li-ion is the fastest growing and most promising
battery chemistry.
The energy density of the Li-ion is typically twice that of the standard NiCd. Improvements in
electrode active materials have the potential of increasing the energy density close to three times
that of the NiCd. In addition to high capacity, the load characteristics are reasonably good and
behave similarly to the NiCd in terms of discharge characteristics (similar shape of discharge
profile, but different voltage). The flat discharge curve offers effective utilization of the stored
power in a desirable voltage spectrum.
The high cell voltage allows battery packs with only one cell. Most of today’s mobile phones
run on a single cell, an advantage that simplifies battery design. To maintain the same power,
higher currents are drawn. Low cell resistance is important to allow unrestricted current flow
during load pulses.
The Li-ion is a low maintenance battery, an advantage that most other chemistries cannot claim.
There is no memory and no scheduled cycling is required to prolong the battery’s life. In
addition, the self-discharge is less than half compared to NiCd, making the Li-ion well suited for
modern fuel gauge applications. Li-ion cells cause little harm when disposed.
Despite its overall advantages, Li-ion also has its drawbacks. It is fragile and requires a protection
circuit to maintain safe operation. Built into each pack, the protection circuit limits the peak
voltage of each cell during charge and prevents the cell voltage from dropping too low on
discharge. In addition, the cell temperature is monitored to prevent temperature extremes. The
maximum charge and discharge current is limited to between 1C and 2C. With these precautions
in place, the possibility of metallic lithium plating occurring due to overcharge is virtually
eliminated.

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Aging is a concern with most Li-ion batteries and many manufacturers remain silent about this
issue. Some capacity deterioration is noticeable after one year, whether the battery is in use or
not. Over two or perhaps three years, the battery frequently fails. It should be noted that other
chemistries also have age-related degenerative effects. This is especially true for the NiMH if
exposed to high ambient temperatures.
Storing the battery in a cool place slows down the aging process of the Li-ion (and other
chemistries). Manufacturers recommend storage temperatures of 15°C (59°F). In addition, the
battery should be partially charged during storage.
Manufacturers are constantly improving the chemistry of the Li-ion battery. New and enhanced
chemical combinations are introduced every six months or so. With such rapid progress, it is
difficult to assess how well the revised battery will age.
The most economical Li-ion battery in terms of cost-to-energy ratio is the cylindrical 18650 cell.
This cell is used for mobile computing and other applications that do not demand ultra-thin
geometry. If a slimmer pack is required (thinner than 18 mm), the prismatic Li-ion cell is the
best choice. There are no gains in energy density over the 18650, however, the cost of obtaining
the same energy may double.
For ultra-slim geometry (less than 4 mm), the only choice is Li-ion polymer. This is the most
expensive system in terms of cost-to-energy ratio. There are no gains in energy density and the
durability is inferior to the rugged 18560 cell.
The Li-polymer differentiates itself from other battery systems in the type of electrolyte used.
The original design, dating back to the 1970s, uses a dry solid polymer electrolyte. This
electrolyte resembles a plastic-like film that does not conduct electricity but allows an exchange
of ions (electrically charged atoms or groups of atoms). The polymer electrolyte replaces the
traditional porous separator, which is soaked with electrolyte.
The dry polymer design offers simplifications with respect to fabrication, ruggedness, safety and
thin-profile geometry. There is no danger of flammability because no liquid or gelled electrolyte
is used. With a cell thickness measuring as little as one millimeter (0.039 inches), equipment
designers are left to their own imagination in terms of form, shape and size.
Technical difficulties and delays in volume manufacturing have deferred the introduction of the
Li-ion polymer battery. In addition, the promised superiority of the Li-ion polymer has not yet
been realized. No improvements in capacity gains are achieved — in fact, the capacity is slightly
less than that of the standard Li-ion battery.

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2.4 Advantages and Limitations of Li-ion Batteries
Lithium ion battery Advantages
 High energy density: The much greater energy density is one of the chief advantages
of a lithium ion battery or cell. With electronic equipment such as mobile phones needing
to operate longer between charges while still consuming more power, there is always a
need to batteries with a much higher energy density. In addition to this, there are many
power applications from power tools to electric vehicles. The much higher power density
offered by lithium ion batteries is a distinct advantage.
 Self-discharge: One issue with batteries and ells is that they lose their charge over time.
This self-discharge can be a major issue. One advantage of lithium ion cells is that their
rate of self-discharge is much lower than that of other rechargeable cells such as Ni-Cad
and NiMH forms.
 No requirement for priming: Some rechargeable cells need to be primed when they
receive their first charge. There is no requirement for this with lithium ion cells and
batteries.
 Low maintenance: One major lithium ion battery advantage is that they do not require
and maintenance to ensure their performance. Ni-Cad cells required a periodic discharge
to ensure that they did not exhibit the memory effect. As this does not affect lithium ion
cells, this process or other similar maintenance procedures are not required.
 Variety of types available: There are several types of lithium ion cell available. This
advantage of lithium ion batteries can mean that the right technology can be used for the
particular application needed. Some forms of lithium ion battery provide a high current
density and are ideal for consumer mobile electronic equipment. Others are able to
provide much higher current levels and are ideal for power tools and electric vehicles.

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Lithium ion battery Limitations
 Protection required: lithium ion cells and batteries are not as robust as some other
rechargeable technologies. They require protection from being over charged and
discharged too far. In addition to this, they need to have the current maintained within
safe limits. Accordingly one lithium ion battery disadvantage is that they require
protection circuitry incorporated to ensure they are kept within their safe operating limits.
Fortunately with modern integrated circuit technology, this can be relatively easily
incorporated into the battery, or within the equipment if the battery is not
interchangeable.
 Ageing : One of the major lithium ion battery disadvantages for consumer electronics
is that lithium ion batteries suffer from ageing. Not only is this time or calendar
dependent, but it is also dependent upon the number of charge discharge cycles that the
battery has undergone. When a typical consumer lithium cobalt oxide, LCO battery or
cell needs to be stored it should be partially charged - around 40% to 50% and kept in a
cool storage area. Storage under these conditions will help increase the life.
 Transportation: Another disadvantage of lithium ion batteries is that there can be
certain restrictions placed on their transportation, especially by air. Although the batteries
that could be taken in aircraft carry-on luggage are unlikely to be affected, care should
be taken not to carry any more lithium ion batteries than are needed. Any carried
separately must be protected against short circuits by protective covers, etc.
 Cost: A major lithium ion battery disadvantage is their cost. Typically they are around
40% more costly to manufacture than Nickel cadmium cells. This is a major factor when
considering their use in mass produced consumer items where any additional costs are a
major issue.
 Immature technology: Lithium ion battery technology is a developing area. This can
be a disadvantage in terms of the fact that the technology does not remain constant.
However as new lithium ion technologies are being developed all the time, it can also be
an advantage as better solutions are coming available.

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3. THE RECHARGEABLE REVOLUTION
The mobile world depends on lithium-ion batteries — today's ultimate rechargeable energy store.
Last year, consumers bought five billion Li-ion cells to supply power-hungry laptops, cameras,
mobile phones and electric cars. “It is the best battery technology anyone has ever seen,” says
George Crabtree, director of the US Joint Center for Energy Storage Research (JCESR), which
is based at the Argonne National Laboratory near Chicago, Illinois. But Crabtree wants to do
much, much better.
Modern Li-ion batteries hold more than twice as much energy by weight as the first commercial
versions sold by Sony in 1991 — and are ten times cheaper. But they are nearing their limit.
Most researchers think that improvements to Li-ion cells can squeeze in at most 30% more
energy by weight. That means that Li-ion cells will never give electric cars the 800-kilometre
range of a petrol tank, or supply power-hungry smartphones with many days of juice.
In 2012, the JCESR hub won US$120 million from the US Department of Energy to take a leap
beyond Li-ion technology. Its stated goal was to make cells that, when scaled up to the sort of
commercial battery packs used in electric cars, would be five times more energy dense than the
standard of the day, and five times cheaper, in just five years. That means hitting a target of 400
watt-hours per kilogram (Wh kg−1
) by 2017.
Crabtree calls the goal “very aggressive”; veteran battery researcher Jeff Dahn at Dalhousie
University in Halifax, Canada, calls it “impossible”. The energy density of rechargeable batteries
has risen only six fold since the early lead–nickel rechargeable of the 1900s. But, says Dahn, the
JCESR's target focuses attention on technologies that will be crucial in helping the world to
switch to renewable energy sources — storing up solar energy for night-time or a rainy day, for
example. And the US hub is far from alone. Many research teams and companies in Asia, the
Americas and Europe are looking beyond Li-ion, and are pursuing strategies that may topple it
from its throne.
Five years ago, Wilcke, who heads IBM's Nano science and technology division in San Jose,
California, launched a project to develop a car battery with an 800-kilometre range. At the start,
he focused on the theoretical ultimate in energy-dense electrochemical storage: the oxidation of
lithium with oxygen drawn from the air. Such 'breathing' batteries have a huge weight advantage
over other types, because they do not have to carry around one of their main ingredients. A
lithium–oxygen (Li–O) battery can, in theory, store energy as densely as a petrol engine — more
than ten times better than today's car battery packs.

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Source: http://www.nature.com/news/the-rechargeable-revolution-a-better-battery-1.14815
Persson and Gerbrand Ceder, a materials scientist at the Massachusetts Institute of Technology
in Cambridge, founded a company to develop these higher-charge-carrying batteries. Pellion
Technologies, based in Cambridge, is tight-lipped about its results; it has published only one
paper about electrolytes2
. A spate of patents published in late 2013 hint that the company is
developing more-open electrode structures to help the magnesium ions to flow. Major electronics
firms such as Toyota, LG, Samsung and Hitachi are also working on such cells, releasing little
information beyond occasional teasers.
As companies jostle in secret, Persson continues to run through what she calls the “electrolyte
genome”. The sifting-by-supercomputer approach could also help the search for batteries made
with other multiple-charge-carrying (or 'multivalent') metals, such as aluminum and calcium.
Ceder urges patience, pointing out that research into Li-ion battery chemistry has enjoyed a 40-
year head start. “We have so little information about multivalent ions,” he says.

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3. FUTURE OF BATTERIES DEVELEVOPMENT
3.1 Na-ion Rechargeable Battery
At the end of November a team of French researchers from the CNRS, the French National
Centre for Scientific Research and the CEA, France's Alternative Energies and Atomic Energy
Commission, announced in a press release and a CNRS News article that they had produced, in
collaboration with the Research Network on Electrochemical Energy Storage, RS2E, a prototype
sodium-ion battery that can store an acceptable amount of electricity in the same standard
industry format as lithium ion batteries. It is slightly larger than an AA battery—18 mm x 65
mm.
Sodium has a very similar chemistry to lithium, and as soon as lithium-ion batteries came
to market, researchers started looking to sodium as a substitute for lithium in rechargeable
batteries. Unlike lithium, the reserves of sodium are practically unlimited. The highest hurdle for
sodium to clear on its way to battery dominance is the development of suitable electrodes.
Although the news article calls the composition of the negative electrode "a trade secret," the
team applied for a patent in October of this year, describing a negative electrode with a layered
structure based on the titanium oxide compound Na2Ti3O7, and a method to produce it.
Such electrode structures can store lithium ions, and recently researchers have begun
investigating their suitability for storing sodium ions.
"The chemistry is very close to that of the lithium battery, and from that point of view there are
no major difficulties; the mechanisms are the same ones and all the industrial processes for their

18. 18
production are the same," says Laurence Croguennec, a material scientist at the CNRS Institut
de Chimie de la Matière Condensée de Bordeaux.
One remaining problem is that sodium is less efficient as a charge carrier. "A sodium battery
loses 0.3 volts as to compared to a lithium battery. You have to develop materials that can
function at higher voltages and that provide ample capacity," says Croguennec.
Whether sodium-ion batteries will reach parity with lithium-ion batteries is still an open
question. "The development of the electrode has taken six months, so this gives us hope for
improvement. The performance that has been announced is quite good for a starting point, and
materials can be further optimized," says Croguennec. For the moment the sodium batteries have
a storage capacity of 90Wh/kg, which is comparable to the early lithium batteries.
Lithium-ion batteries are everywhere, powering phones, cars, and avionics, among other
things. However, lithium is a relatively rare element, found in some locations in South America.
That not only keeps the price of lithium-ion batteries high, but also makes the supply chain
vulnerable to political instabilities.
Graphene Composite Offers Critical Fix for Sodium-ion Batteries
(source: http://spectrum.ieee.org/nanoclast/semiconductors/nanotechnology/graphene-composite-offers-critical-fix-for-
sodiumion-batteries)
Sodium has a very similar chemistry to lithium, and as soon as lithium-ion batteries came
to market, researchers started looking to sodium as a substitute for lithium in rechargeable
batteries. Unlike lithium, the reserves of sodium are practically unlimited. The highest hurdle for
sodium to clear on its way to battery dominance is the development of suitable electrodes.
At the end of November a team of French researchers from the CNRS, the French National
Centre for Scientific Research and the CEA, France's Alternative Energies and Atomic Energy
Commission, announced in a press release and a CNRS News article that they had produced, in
collaboration with the Research Network on Electrochemical Energy Storage, RS2E, a prototype
sodium-ion battery that can store an acceptable amount of electricity in the same standard

19. 19
industry format as lithium ion batteries. It is slightly larger than an AA battery—18 mm x 65
mm.
Although the news article calls the composition of the negative electrode "a trade secret," the
team applied for a patent in October of this year, describing a negative electrode with a layered
structure based on the titanium oxide compound Na2Ti3O7, and a method to produce it.
Such electrode structures can store lithium ions, and recently researchers have begun
investigating their suitability for storing sodium ions.
"The chemistry is very close to that of the lithium battery, and from that point of view there are
no major difficulties; the mechanisms are the same ones and all the industrial processes for their
production are the same," says Laurence Croguennec, a material scientist at the CNRS Institut
de Chimie de la Matière Condensée de Bordeaux.
One remaining problem is that sodium is less efficient as a charge carrier. "A sodium battery
loses 0.3 volts as to compared to a lithium battery. You have to develop materials that can
function at higher voltages and that provide ample capacity," says Croguennec.
Whether sodium-ion batteries will reach parity with lithium-ion batteries is still an open
question. "The development of the electrode has taken six months, so this gives us hope for
improvement. The performance that has been announced is quite good for a starting point, and
materials can be further optimized," says Croguennec. For the moment the sodium batteries have
a storage capacity of 90Wh/kg, which is comparable to the early lithium batteries.
"We are not yet close to the energy levels that you can find, for example, in Tesla cars," says
Croguennec. At this point, the most reasonable application for sodium batteries is renewable
energy storage, as they could be cheaper per stored unit of energy and are scalable in size
like lithium batteries, explains Croguennec.
The prototypes are not yet ready for the market, but CEA believes they will be of interest to
industry. “We are now in discussion with possible industrial partners, says Croguennec.

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5. SODIUM AS A SUBSTITUE OF LITHIUM
Sodium-ion batteries offer an attractive alternative to Li-ion batteries not because they
outperform Li-ion batteries, but mainly because of lower costs due to the the nearly unlimited
supply of sodium. They are also an attractive alternative in part because unlike their sodium-
sulfur battery cousins they can be made in similar sizes to Li-ion batteries.
However, the commercial development of sodium-ion batteries has been hampered by the
materials used in the negative electrodes. These swell to as much as 400 to 500 percent their
original size, leading to mechanical damage and loss of electrical contact
Now researchers at Kansas State University have developed a composite, paper-like material
made from two 2-dimensional materials—molybdenum disulfide and graphene Nano sheets—
that has been shown to overcome this shortcoming.
In research published in the journal ACS Nano (“MoS2/Graphene Composite Paper for Sodium-
Ion Battery Electrodes”), the 2-D composite material developed proved resistant to the
“alloying” reaction that electrode materials typically suffer when in contact with sodium.
The research also marks the first time that the flexible paper electrode was used in an anode for
sodium-ion battery that operates at room temperature.
The Kansas State researchers began their work by looking for better ways to synthesize 2-D
materials for rechargeable battery applications. This led them to create the large-area composite
paper that they used for negative electrodes.
The paper is a composite of acid-treated layered molybdenum disulfide and chemically modified
graphene in an interleaved structured. “The interleaved and porous structure of the paper
electrode offers smooth channels for sodium to diffuse in and out as the cell is charged and
discharged quickly,” said Gurpreet Singh, an assistant professor at Kansas State and one of the
authors of the paper, in a press release. “This design also eliminates the polymeric binders and
copper current collector foil used in a traditional battery electrode.”
While the researchers are looking for opportunities to commercialize their technology for
rechargeable battery applications, they also feel that they have contributed to the fundamental
understanding of how to synthesize 2-D materials.
This method should allow synthesis of gram quantities of few-layer-thick molybdenum disulfide
sheets, which is very crucial for applications such as flexible batteries, super capacitors, and
polymer composites,”

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6. CONCLUSION
The first prototype of a sodium-ion battery has been revealed on 3rd
December 2015 by the RS2E,
a French network bringing together researchers and industrial actors. This technology, inspired
by the lithium-ion batteries already used in portable computers and electric vehicles, could lead
to the mass storage of intermittent renewable energy sources.
The announcement should cause a stir in the highly competitive world of batteries. French
researchers from the RS2E network1 on 3rd
December 2015 revealed the first prototype of the
sodium-ion "18650" battery, a standard format used notably in portable computers. The
information may not sound exciting to non-specialists. Yet scientists across the globe, including
the US, Japan, the UK, and Israel, are working on this technology which today is considered the
most serious alternative to the lithium-ion batteries that equip practically all portable electronic
devices (portable computers, tablets, smartphones...) and are beginning to take a serious look at
electric vehicles. The battery used for Tesla cars, for example, is nothing more than the
combination of several thousand "18650" lithium-ion batteries.
It's an ongoing revolution, "It's a critical piece in the whole puzzle in how we stop burning fossil
fuels completely."

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9. REFERENCES
1. http://spectrum.ieee.org/energywise/energy/renewables/a-first-prototype-of-a-sodiumion-
rechargeable-battery
2. http://feeds.feedburner.com/IeeeSpectrumEnergywiseBlog
3. http://spectrum.ieee.org/nanoclast/semiconductors/nanotechnology/graphene-composite-
offers-critical-fix-for-sodiumion-batteries
4. http://spectrum.ieee.org/tag/Li-ion+batteries/?media=all&offset=0&sortby=desc
5. http://www.energie-rs2e.com/en/news/na-ion-batteries-promising-prototype
6. http://www.nature.com/news/the-rechargeable-revolution-a-better-battery-1.14815
7. https://en.wikipedia.org/wiki/Rechargeable_battery
8. https://en.wikipedia.org/wiki/Battery_(electricity)
9. http://www.radio-electronics.com/info/power-management/battery-technology/lithium-ion-
battery-advantages-disadvantages.php
10. http://spectrum.ieee.org/tag/graphene/?media=all&offset=0&sortby=desc