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The battery in your phone traces back to an idea Stanley Whittingham turned into hardware in the early 1970s: a layered solid can soak up lithium ions and give them back. The Nobel Prize popular information for 2019 says Whittingham developed "the first functional lithium battery" by pairing a lithium anode with a titanium disulphide cathode.
What did Stanley Whittingham build in the 1970s?
Whittingham moved to Exxon in 1972 from Stanford University, where he had studied solids with atom-sized spaces that charged ions can enter, according to the Nobel Prize popular information. At Exxon he and his colleagues studied superconducting materials such as tantalum disulphide and found that, with potassium ions inside, it gave a couple of volts. Tantalum is heavy, so he swapped it for titanium, a lighter element with similar properties.
He published the result in Science on 11 June 1976 as Electrical Energy Storage and Intercalation Chemistry. The abstract says the reaction of layered titanium disulphide with lithium "occurs very rapidly and in a highly reversible manner at ambient temperatures as a result of structural retention." In plain words: it runs backwards for recharging and the solid keeps its shape.
The Royal Swedish Academy of Sciences' scientific background on the 2019 prize gives the numbers:
The cell had a lithium metal anode, a TiS₂ cathode and an emf of 2.5 V.
A test cell was cycled 1,100 times without significant loss of reversibility.
How does titanium disulphide store lithium between its layers?
Titanium disulphide is a stack of sandwiches: a sheet of titanium atoms held between two sheets of sulphur atoms, with weak van der Waals gaps between one sandwich and the next. The Nobel scientific background explains that Whittingham and Fred Gamble showed lithium can enter LiₓTiS₂ over the whole range 0 < x ≤ 1, with lithium ions progressively filling octahedral sites in those gaps.
Intercalation is the reversible insertion of guest ions into spaces inside a solid host whose structure stays intact. For Whittingham's cell the discharge reaction is x Li + TiS₂ → LiₓTiS₂ (Nobel scientific background).
During discharge, lithium at the anode gives up electrons. The Li⁺ ions cross the electrolyte and slide into the gaps, while the electrons travel through the wire to the cathode. Charging pushes both back. You can check the bookkeeping yourself: with lithium at +1 and sulphur at −2, titanium must go from +4 in TiS₂ to +3 in LiTiS₂.
The host changes only a little. X-ray diffraction measurements by Houdeville and colleagues (2021) put the layer repeat distance c at 5.700 Å in fresh TiS₂ and 6.187 Å at the end of lithium insertion, close to LiTiS₂: an expansion of about 8.5%. The Nobel popular information notes that earlier rechargeable electrodes broke down by reacting with the electrolyte, while Whittingham's cell stored lithium ions in spaces inside the titanium disulphide.
Why didn't Whittingham's lithium battery go on sale widely?
According to the Nobel popular information, repeated charging grew thin whiskers of lithium from the anode; when they reached the other electrode the cell short-circuited and could catch fire. Adding aluminium to the lithium and changing the electrolyte helped, and the battery was made on a small scale for a Swiss clockmaker's solar-powered timepieces. When oil prices fell in the early 1980s, Exxon cut back and licensed the technology to three companies.
John Goodenough then replaced the sulphide with lithium cobalt oxide and reached four volts (see Goodenough's cobalt oxide cathode), and Akira Yoshino removed pure lithium from the cell (see how Yoshino built the first safe lithium-ion battery). The three shared the 2019 Nobel Prize in Chemistry "for the development of lithium-ion batteries".
How much charge can titanium disulphide hold?
With Class 12 electrochemistry you can find the most charge one gram of TiS₂ can take, if every formula unit accepts one lithium (x = 1).
Molar mass. Titanium's standard atomic weight is 47.867 (CIAAW) and sulphur's lies between 32.059 and 32.076 (CIAAW). Using 32.06, M(TiS₂) = 47.867 + 2 × 32.06 = 111.99 g/mol.
Electrons. One Li⁺ in means one electron through the wire, so 111.99 g of TiS₂ takes 1 mol of electrons.
Charge. The Faraday constant is 96,485 C/mol (NIST), so one gram takes 96,485 ÷ 111.99 = 861.6 C.
Convert. 1 mAh is 3.6 C, so 861.6 ÷ 3.6 ≈ 239 mAh per gram.
Energy. Multiply by voltage. The Nobel popular information says Whittingham's battery generated more than two volts; at 2 V that is about 479 mWh per gram, or roughly 480 Wh per kilogram of TiS₂.
That is for the cathode material alone; a real cell also carries lithium, electrolyte and casing, so it stores far less per kilogram. If coulombs to mAh feels shaky, our guide to converting battery mAh to coulombs and moles of electrons goes through it slowly.
For more practice, the Fermi Problem Library has worked problems with a step-by-step solver that explains the reasoning rather than printing an answer, and the Fermi Simulation Lab has interactive simulations for ideas that are easier to see than to read.
