nobel-prize-for-chemistry

Context: The 2019 Nobel Prize for Chemistry was awarded for working towards the development of practical lithium-ion batteries

Lithium-ion batteries & Whittingham’s Contribution

  • Since the early 19th century, chemical batteries have been around. They consist of two electrodes between which electrons flow and generate a current. 
  • The challenge of such batteries is to choose appropriate electrodes and electrolyte, which mediates the current, and generate sufficient current safely at room temperature without occupying too much space.
  • Lead acid batteries still used in cars to start engines and power headlights and power windows are too bulky to practically function as car engines. 
  • Exxon, which was worried about depleting oil stocks, commissioned top researchers to find alternatives to fossil fuels. Whittingham, studied solid materials whose atoms had spaces between them. 
  • Fitting positively charged ions in them, a process called intercalation changed their properties and Whittingham found that potassium ions when intercalated in titanium made for an extremely energy-dense material. Lithium is also a light element and useful as an electrode, he found. 
  • In a battery, electrons should flow from the negative electrode - the anode to the positive - the cathode. Therefore, the anode should contain a material that easily gives up its electrons and lithium releases electrons willingly. This made for an ideal battery.

 

About lithium-ion batteries

  • Although slightly lower in energy density than lithium metal, lithium-ion is safe, provided certain precautions are met when charging and discharging.
  • In 1991, the Sony Corporation commercialized the first lithium-ion battery. Other manufacturers followed suit.
  • These batteries are the edifice of the wireless technology revolution that made possible portable compact disc players, digital wrist watches, laptops and mobile phones of today.
  • It is also seen as important to a fossil-free future of electric cars that governments envisage to address climate change.

 Why are they important?

  1. The energy density of lithium-ion is typically twice that of the standard nickel-cadmium.
  2. The load characteristics are reasonably good and behave similarly to nickel-cadmium in terms of discharge.
  3. The high cell voltage of 3.6 volts allows battery pack designs with only one cell.
  4. Lithium-ion is a low maintenance battery, an advantage that most other chemistries cannot claim.
  5. There is no memory and no scheduled cycling is required to prolong the battery’s life.
  6. In addition, the self-discharge is less than half compared to nickel-cadmium, making lithium-ion well suited for modern fuel gauge applications.
  7. lithium-ion cells cause little harm when disposed.

Limitations:

  1. It is fragile and requires a protection circuit to maintain safe operation.
  2. Aging is a concern with most lithium-ion batteries.
  3. Some capacity deterioration is noticeable after one year, whether the battery is in use or not.
  4. Expensive to manufacture – about 40 percent higher in cost than nickel-cadmium.
  5. Not fully mature – metals and chemicals are changing on a continuing basis.

About Lithium:

  • It is a rare and the lightest known metal.
  • Lithium makes up a mere 0.0007 percent of the Earth's crust.
  • symbol Li and atomic number 3.
  • Like all alkali metals, lithium is highly reactive and flammable and must be stored in mineral oil.
  • Lithium has the greatest electrochemical potential and provides the largest energy density for weight.

Application of Lithium:

  • It's used in the manufacture of aircraft and in certain batteries. 
  • It's also used in mental health: Lithium carbonate is a common treatment of the bipolar disorder, helping to stabilize wild mood swings caused by the illness. 
  • Lithium-ion batteries are the key to lightweight, rechargeable power for laptops, phones, and other digital devices.

Contributions of Goodenough and Yoshino

  • Goodenough had set to work on improving Whittingham’s battery. He eventually found that the cathode could have a higher potential if it was built using a metal oxide instead of a metal sulphide. 
  • The challenge for Goodenough and his colleagues was to find a metal oxide that produced a high voltage when it intercalated lithium ions, but which did not collapse when the ions were removed. 
  • Eventually they chanced upon a battery with lithium cobalt oxide in the cathode, which was almost twice as powerful as Whittingham’s battery.
  • Goodenough’s major insight was that batteries did not have to be manufactured in their charged state, as had been done previously. Instead, they could be charged afterwards.