lithium versus lithium ion – the difference is in the anode

7/28/2019 Lithium versus Lithium Ion The difference is in the Anode

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Lithium versus Lithium Ion The

difference is in the Anode

Posted on November 2, 2009

Metallic lithium rechargeable battery

technology was first developed prior to 1970

and is still being pursued today by companies

such as the Bollor Group of France who

recently acquired Avestor from Hydro Quebec in March of 2007 and Sion Power of Arizona

with their Lithium Sulfur system. The defining aspect of lithium battery technology is that

the anode itself is made of pure lithium metal in the form of a foil. During discharge, lithium

ions dissolve from the surface of the foil and transfer to the cathode via the electrolyte.

During charge, the lithium ions transfer back to the anode to be electroplated back onto the

surface of the lithium foil, reforming as pure lithium metal once again, losing their status as

ions.

Benefits of metallic lithium anodes are they are light weight and have high reversible

capacity of 3,860 mAh/g. Problems are they are highly alkali in nature causing them to

react with the organic electrolyte forming a passivation layer on their surface which leads to

non-uniform plating of lithium during the charging process and formation of dendrites

causing short circuits and serious safety problems due to localized hot spots. To overcome

these problems, researchers in the 1970s began studying the use of anode intercalation

materials to replace metallic lithium. The new anode materials operate in the same fashion

as existing cathode materials in that they hold the lithium atoms by insertion site diffusion,

except that the anode materials do it at a much lower voltage closer to that of metallic

lithium. Hence the lithium ion battery was born, where lithium atoms remain separate

from one another at all times while residing in either the anode or cathode electrodes,

eliminating the trouble of uneven metallic plating and its associated problems.

Lithium ion cells are termed rocking-chair cells because the lithium ions rock back and

forth during charging and discharging between the anode and the cathode intercalation

materials. Anode intercalation materials have much lower reversible capacities compared

to metallic lithium, but the benefits of improved safety and much higher cycle life quickly

outweigh the drawbacks in most applications.

The electrochemical potential of anode and cathode materials are measured relative to pure

metallic lithium reference electrodes representing zero Volts, such that when a cell is

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2 THOUGHTS ON LITHIUM VERSUS LITHIUM ION T HE DIFFERENCE IS IN THE ANODE

constructed from an anode material with 0.3 Volts potential and a cathode material with 4.0

Volts potential, relative to metallic lithium, the resulting cell voltage is calculated by the

difference, 4.00.3=3.7 Volts.

The most common anode material in use today is carbon in its layered form as graphite or

in its glassy amorphous form as hard carbon. Carbon is cheap, light, environmentally

friendly, has high reversible capacity of 372 mAh/g, excellent cycling characteristics, and

low electrochemical potential relative to metallic lithium in the range of 0.2-1.0 Volts,

helping to maintain an overall high cell voltage when mated with other various cathode

materials. Problems with carbon anodes are they are voluminous and have high irreversible

first charge capacity loss in the range of 20%.

A less popular anode intercalation material is l ithium titanate used by Toshiba and

Altairnano, these metal oxide materials have low capacities of only 150 mAh/g and high

electrochemical potentials of around 1.5 Volts resulting in a much lower energy density

cell. Benefits are very good cycle life, stable electrolyte, and high power characteristics.

New silicon anode materials have very high theoretical capacities up to 4,200 mAh/g,

exceeding that of even pure lithium, and voltage potentials below 1.0 Volts, but suffer from

high mechanical stressing during the lithiation-delithiation processes, resulting in rapidly

fading capacity loss during cycling. Other promising areas for new anode material

developments include other silicides, nitrides, and lithium metal alloys.

This entry was posted in Education by admin. Bookmark the permalink

[http://batteryblog.ca/2009/11/lithium-versus-lithium-ion-the-difference-is-in-the-

anode/] .

KronA

on November 17, 2009 at 11:31 am said:

Very interesting. Do you have much information on the current proportional costs of

the various types of lithium based cell? I saw a study from 1991 which showed (Ithink) 60% of the raw materials cost was cobalt. I presume a lot of the newer

batteries do away with this to reduce costs?

Randyon November 17, 2009 at 4:26 pm said:

There are a lot of factors that go into the cost of lithium ion battery production such
http://batteryblog.ca/2009/11/lithium-versus-lithium-ion-the-difference-is-in-the-anode/comment-page-1/#comment-18http://www.esi-technology.com/http://batteryblog.ca/2009/11/lithium-versus-lithium-ion-the-difference-is-in-the-anode/comment-page-1/#comment-17http://batteryblog.ca/2009/11/lithium-versus-lithium-ion-the-difference-is-in-the-anode/http://batteryblog.ca/author/admin/http://batteryblog.ca/category/education/


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as input materials, processing, labour, capital costs, etc New cathode materials

for large format cells have moved away from using large amounts of cobalt which

helps to reduce some of the material cost.

lithium versus lithium ion – the difference is in the anode

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