Electric vehicles. Will lithium-ion batteries soon be obsolete?

Predicted to replace lithium-ion batteries, li-metal technology comes up against stability problems that require the development of solid batteries. Korean researchers nevertheless claim to have found a solution that can be applied immediately on an industrial scale.

By

Raphael Desrosiers

Published on
Updated

Lithium-ion batteries now equip the vast majority of electric cars. Maybe not for long…

DR


Research is well underway to develop batteries capable of storing ever more energy, for as long as possible, with the least amount of rare materials. The latest discovery comes from KERI (Korea Electrotechnology Research Institute, the South Korean equivalent of the French CNRS) and concerns li-metal batteries. Presented as the evolution of lithium-ion batteries used today by electric cars (but also and above all by smartphones, laptops, etc.), li-metal batteries are often assimilated to solid batteries because their stability seemed can be solved only by the presence of a solid electrolyte. The results of the KERI team’s research seem to have identified a solution guaranteeing stability without a solid electrolyte.

Short course in physics and chemistry

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By occupying the same space, li-metal batteries promise up to twice as much autonomy.

Volvo

To understand the issues behind this discovery, it is necessary to go into more detail about how batteries work. By popularizing, the batteries work thanks to the circulation of a current between a positive pole and a negative pole. Concretely, these two poles take the form of electrodes, each made of a different material. For lithium-ion batteries, this is a metal cathode (positive electrode) containing lithium and an anode (negative electrode) made of graphene. These two electrodes are bathed in a liquid called electrolyte, which transfers energy from one electrode to the other (to generate an electric current). Problem: Graphene is not easy to obtain, and its ability to store electricity is not the best compared to other metals. Why is it then used? Because it allows a certain stability against lithium, which tends to self-destruct during charging and discharging due to the formation of dendrites, kinds of residues which limit the conductivity of the electrodes and cause short circuits.

Solid state batteries and li-metal batteries

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CNRS sodium battery

Several technologies are competing to replace lithium-ion.

YouTube CNRS

Solid-state batteries use an electrolyte no longer in liquid but solid form, to limit the formation of these dendrites. From there, it is possible to do without graphene to use other denser materials (capable of storing more electricity) such as… lithium. This is the principle of li-metal batteries, which therefore have a lithium anode. This theoretically makes it possible to store almost twice as much electricity as a lithium-ion battery, while aging less quickly because fewer dendrites are generated thanks to the solid electrolyte. The confusion between solid batteries and li-metal batteries comes from there, but there are solid batteries which use other metals such as LMP (lithium-metal-polymer) from BollorĂ©, which fitted the Autolib’. On the other hand, non-solid li-metal batteries were not considered.

A new technology that could be quickly implemented?

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wildcat solid battery

Many players are engaged in solid-state batteries such as Wildcat and Kodak, which plan to sell them from 2024.

DR

Yet this is the track explored by KERI researchers, who managed to operate li-metal batteries with liquid electrolyte by covering the anode with a sheet composed of a mixture of carbon and gold nanoparticles. To simplify, the carbon prevents the formation of dendrites, and the gold ensures good electrical conductivity. Result, a li-metal battery which could be produced much faster than solid batteries and with the industrial tool in place. An exciting promise made by the researchers and which could therefore quickly double the capacity of the batteries while extending their lifespan and doing without graphene (but not gold suddenly). It remains to be seen whether this solution can actually be used en masse and whether its cost will be competitive with that of solid-state batteries, planned for 2024.

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