25 Oct 2019

Chemistry Nobel Prize, 20193 min read

Source : The Hindu

Manifest pedagogy: This is the second article of Noble prizes 2019 after physiology. In the march towards energy efficiency Lithium-Ion batteries have made a revolution. The discovery is recognised only off late. The specifications and performance of these batteries is very important for Prelims.

In news: Nobel prize, 2019 for chemistry has been awarded recently.

Placing it in syllabus: Recent discoveries in S&T (explicitly mentioned)

Dimensions:

  • Science behind lithium ion batteries
  • Applications
  • Comparison with other batteries

Content: The 2019 Nobel Prize in Chemistry has been awarded to John B. Goodenough, M. Stanley Whittingham and Akira Yoshino “for the development of lithium-ion batteries“.

Science behind lithium ion batteries: At the time, it was assumed that metallic lithium should serve as the anode in the batteries special focus was put on identifying matching cathode materials. Those materials with high reduction potential that were able to accommodate lithium ions at high transfer rates were of special interest. 

Titanium disulfide (TiS2) was shown to be able to host lithium ions by Walter Rüdorff in 1965. This structure was lamellar with TiS2 arranged in layers, between which lithium ions could become intercalated. 

The intercalation effect was further demonstrated by M. Stanley Whittingham and his team who showed that lithium can be chemically intercalated in the LixTiS2 material. Hence he used extremely energy rich TiS2 to create an innovative cathode in a lithium battery. 

The battery’s anode was partially made from metallic lithium, which has a strong drive to release electrons. This resulted in a battery that literally had great potential, just over two volts. A working, rechargeable battery was subsequently demonstrated in 1976. However, metallic lithium is reactive and the battery was too explosive to be viable.      

Lithium-based battery using LixTiS2 as the cathode

John Goodenough predicted that the cathode would have even greater potential if it was made using a metal oxide instead of a metal sulphide. In 1980 he demonstrated that cobalt oxide (CoO2) with intercalated lithium ions can produce as much as four volts which would lead to much more powerful batteries.

Lithium-based battery using LixCoO2 as the cathode

With Goodenough’s cathode as a basis, Akira Yoshino created the first commercially viable lithium-ion battery in 1985. Instead of using reactive lithium in the anode, he used petroleum coke, which like the cathode’s cobalt oxide, can intercalate lithium ions.

Ion transfer cell lithium-ion battery configuration

These discoveries and developments ultimately led to the release of a commercial lithium battery in 1991 which was a lightweight, hardwearing battery that could be charged hundreds of times before its performance deteriorated. 

The advantage of lithium-ion batteries is that they are not based upon chemical reactions that break down the electrodes, but upon lithium ions flowing back and forth between the anode and cathode.

Chemical properties of Li:

  • With atomic number 3, lithium is the lightest metal with a density of only 0.53 g/cm3. 
  • It also has a very low standard reduction potential, thus making it suitable for high-density, high-voltage battery cells.
  • Lithium is a relatively reactive metal, which has to be protected from water and air.

Applications:

  • Power backups/UPS
  • Mobile, Laptops, and other commonly used consumer electronic goods
  • Electric mobility
  • Surveillance systems
  • Energy Storage Systems (solar, wind)
  • Light and reliable marine performance 

Comparison with other batteries:

Nickel Cadmium (NiCd) – has relatively low energy density. The NiCd is used where long life, high discharge rate and economical price are important. Main applications are two-way radios, biomedical equipment, professional video cameras and power tools. The NiCd contains toxic metals and is environmentally unfriendly.

Nickel-Metal Hydride (NiMH) – has a higher energy density compared to the NiCd at the expense of reduced cycle life. NiMH contains no toxic metals. Applications include mobile phones and laptop computers.

Lead Acid – most economical for larger power applications where weight is of little concern. Used for hospital equipment, wheelchairs, emergency lighting and UPS systems.

Lithium Ion (Li‑ion) – fastest growing battery system. Is used where high-energy density and lightweight is of prime importance. The technology is fragile and a protection circuit is required to assure safety. 



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