Sunday, April 13, 2014

Beware BBC Business Editors who think they can write about science.

One of my perennial moans on this site is the hijacking of science reporting by media folk who think they can get their heads round science, but can't. The latest is Laurence Knight, Business Editor of the BBC, writing just two days ago on the use of lithium in rechargeable mobile phone batteries.

The title itself was an immediate giveaway. The lithium that is in the RECHARGEABLE cells of our lithium ION batteries does NOT power them. It's the electric current used for initial charging and subsequent recharging that powers them. The lithium supplies NO chemical and/or electrochemical energy to the uncharged cells. It's there purely a carrier and concentrator of externally-supplied electrical energy.

Pedantic? Maybe. But there's a common source of confusion about lithium in batteries, depending on whether the battery is PRIMARY (non-rechargeable) or SECONDARY (rechargeable).

One can and does have lithium metal, comprising lithium atoms, in a type of primary cell, and yes, it does take advantage of the exceptionally electropositive nature of lithium, the ELEMENT, which is the first member of the reactive alkali metals (though as the article points out, not as reactive as sodium or potassium in the same Group 1 of the Periodic Table).  But one would never be able to recharge a lithium primary cell once the metal had turned to a lithium salt (Li  to Li+ plus electron). It's simply not thermodynamically feasible to reverse that reaction under normal conditions of temperature etc..

The lithium ION battery works on an entirely different principle. It does not contain the reactive lithium metal, but lithium ions (chemically no more reactive than the sodium ions in one's table salt). It depends on a subtle effect, namely the penetration of lithium ions by the so-called intercalation effect in cleverly designed matrix materials.

Here's a handy image discovered on the internet:

So, unlike a lithium metal battery, which works without initial charging, the lithium ion battery will not work until it is given its priming charge, which causes those lithium ions to migrate from the positive electrode (left) to the negative electrode (right). Thus the introductory comment that it is not lithium that power this type of battery, but the electrical charge/recharge cycles. Lithium ions act merely as carriers of the externally-supplied electrical energy, albeit ones that can embed into the electrode materials for temporary storage.

So the lithium ion battery does NOT exploit the chemical reactivity of elemental  lithium, so references to the metal are irrelevant and misleading. What it does is to exploit the minute size of lithium ions (lithium comes 3rd in atomic number after hydrogen and helium in the Periodic Table, having just 3 protons and 4 neutrons).

Did Laurence Knight, Business Editor of the BBC, not bother to check his copy with the BBC's Science Editor before submitting for publication? I doubt it. In fact I wonder for how much longer the BBC will bother with a Science Editor when there are generalist liberal arts and finance-based journalists who consider themselves fully up to the task of reporting on scientific and technical matters.

Further reading? Try this for starters.


What is the difference between a “lithium metal battery” and a “lithium ion battery”?

A lithium metal battery (primary) is usually non-rechargeable, contains metallic lithium and features a higher energy density than other non-rechargeable batteries. Lithium metal batteries are often used in calculators, pacemakers, remote car locks and watches, to name a few.
A lithium ion battery (secondary) is rechargeable, does not contain metallic lithium and features high energy density. A lithium polymer battery is considered a type of lithium ion battery. Lithium ion batteries are used in consumer products such as cell phones, electric vehicles, laptop computers, power tools and tablets.


Postscript: internet search:

Laurence Knight's Education (in his own words)

University College London, U. of London

Master's degree, Eastern Europe stuff


University of Oxford

Bachelor's degree, PPE



So, in conclusion,  what might Laurence Knight have said that would accurately convey the flavour of lithium chemistry as applied to the batteries in everyday kit?  Flavour - ah now, there's a handy term.
Lithium comes in two flavours.  Mark 1 lithium atom-powered batteries - with a fiery flavour if you like. Open one of those up (not recommended) and you'll find a metal there so chemically-reactive that it froths when you add water, liberating flammable hydrogen gas. Those batteries have a limited application - since they are not rechargeable,.
What we have in our mobile phones is tamed lithium - lithium ions, which are atoms stripped of a single electron. Think of it as Mark 2 vanilla-flavour lithium.Lithium ions are lithium atoms that have lost their oomph. But they can still be made to serve as workhorses. Sorry about the mixed metaphors.

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