New 'doped' solid-state batteries can charge to 80 per cent in just nine minutes
Success is currently limited to the lab, but findings mark a ‘paradigm shift’ in how battery boffins develop future EV batteries
Professors in China and California have been doping. Not in the ‘competitive athlete’ sense, no – they’ve been applying novel ways to catalyse the chemistry in solid-state lithium-ion batteries and it’s worked out. Their batteries charge reliably to 80 per cent in just nine minutes, and could spell a brighter future for electric car batteries.
And brace yourselves: it's going to take a very high dive into a very deep pool of hardcore ScienceSpeak, and a swim around this fundamental shift and away from this increasingly tortured analogy.
In all the various materials the researchers tested, they found a sulfur-doped phosphorus anode coupled with a lithium cobalt oxide cathode gave the best numbers. Which in Language You Can Understand, saw a 302Wh/kg energy-dense battery gain 80 per cent of its juice back in less than ten minutes.
To put that in context, the Panasonic 21700 cell used in the Tesla Model 3 has a gravimetric energy density of 253Wh/kg, which can be recharged to 80 per cent in roughly 25 minutes. Almost half an hour down to less than ten minutes? Time to get the step-change klaxon going.
To better understand exactly what chemistry makes this kind of leap, let's test your foundation knowledge. You already know a battery has a cathode, anode and electrolyte*, yes? Excellent.
Typically, today's lithium-ion EV batteries are made from a lithium nickel manganese cobalt (Li-NMC) combo or a lithium-iron-phosphate (LFP) combo – those are the elements on the cathode. The anodes are typically made from graphite, silicon, and more recently, labs have been looking into phosphorus ones.
You also know that the electrolyte is either liquid, or (in the very near future) solid-state, and it's present to help the lithium ions move about. Also understand, the presence of cobalt and manganese are there to help stabilise the chemical reaction between other elements. Like the referee in a heavyweight boxing fight, they let the action happen but keep things under control.
Anyway, publishing their 'paradigm-shifting' findings in the Journal of American Chemical Studies, the scientists at the University of Science and Technology in China (USTC) and University of California, used ‘heteroatom-doping’ in a process called ‘electrocatalysis’. Sounds like a really fun Friday night out, no?
Conventionally, that version of catalysing has only been used when there’s a gas or liquid electrolyte – and very rarely a solid-state one. Not any more. [Deep breath] The pivotal ‘heteroatom-doping’ approach devised by these clever folks injected boron into a silicon electrode and sulfur into a phosphorus one, into a battery with a solid electrolyte. Adding those elements weakened the bonds between atoms and enabled the lithium ions to come and join the party faster. And what that means for our tiny minds, is basically Really Fast Charging.
You see, the strong bonds of the electrode material is what slows recharging down, i.e. lithiation (more ScienceSpeak meaning 'becoming lithium-ion-ified') is harder. If it were the nerdiest episode of First Dates, the UK’s loveliest barman Merlin Griffiths would be the dope, using a nice bottle of 2018 vintage chardonnay to bring about chemistry more quickly.
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Obviously, this is all lab-based stuff and it’s much tougher to scale up and roll out in the real world, but it’s useful to know someone values your time, right?
*(and a separator, yes, yes, thank you pedants – though remember, in solid-state batteries, the electrolyte which is made of glass, polymer or ceramic can act as separator too)
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