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?
- The energy density of lithium-ion is typically twice that of the standard nickel-cadmium.
- The load characteristics are reasonably good and behave similarly to nickel-cadmium in terms of discharge.
- The high cell voltage of 3.6 volts allows battery pack designs with only one cell.
- Lithium-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 nickel-cadmium, making lithium-ion well suited for modern fuel gauge applications.
- lithium-ion cells cause little harm when disposed.
- It is fragile and requires a protection circuit to maintain safe operation.
- Aging is a concern with most lithium-ion batteries.
- Some capacity deterioration is noticeable after one year, whether the battery is in use or not.
- Expensive to manufacture – about 40 percent higher in cost than nickel-cadmium.
- Not fully mature – metals and chemicals are changing on a continuing basis.
- 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.