25 Jul,2023

Batteries of tomorrow: solid state or sodium ions?



The spread of e-mobility is closely linked to the recharging experience: the speed of recharging depends on the type of station, but also and above all on the type of battery with which the vehicle is equipped.


Here is an overview of the new technologies that could revolutionise the sector



Batteries are the protagonists of everyday life. Besides being the 'fuel' of electric vehicles, they are found in most everyday devices: smatphones, airpods, computers, watches. The technology used for the batteries of all these objects has long been known: they are lithium-ion batteries, a tried and trusted solution.


But with the advent of mass electric mobility and the need for increasingly high-performance, sophisticated and lightweight batteries to serve our vehicles, the industry has invested heavily in recent years in research into technologies that respond better and better to new market requirements.


So how are lithium batteries evolving?

When one speaks of a new frontier for the battery industry, the first technology one thinks of is solid state. Lightweight, with a higher energy density, high performance and safe, lithium-metal batteries are widely regarded as the breakthrough technology for electric vehicles that are getting closer and closer to conventional ones in terms of mileage and refuelling times.





Technological evolution


But how does this differ from lithium ion?

First of all, there is no single technology, but within the 'solid-state' set there are many products being developed with different characteristics. Generally speaking, solid-state batteries are defined as such because the electrolyte, i.e. the substance used to pass the ions - and thus the charge - between the two poles of the cell is solid or semi-solid, unlike the lithium ion batteries used today, where the electrolyte is liquid and immerses all the components of the cell. The composition of the electrolyte leads to a spatial difference in the cell structure. In lithium-ion cells, the cell consists of an anode (i.e. the negative pole) mostly made up of graphite or carbon, and a positive cathode, made up of different metals according to the different chemistries on the market, mostly NMC (Nickel Manganese Cobalt) and LFP (Lithium Iron Phosphate) in vehicles and LCO (Lithium Cobalt Oxide) in electronic devices. At the ends of the two electrodes is a metal current collector.


To mechanically separate the two electrodes and thus prevent short-circuiting, on the other hand, there is a separator, i.e. an insulator consisting of a very thin layer of plastic polymer with a porous consistency. As explained above, the entire cell is then permeated by an organic liquid electrolyte containing lithium salt through which the ions move, which in the charging and discharging phases pass from one electrode to the other, inserting themselves from time to time into the structures of which they are composed.


In the solid-state battery, the structure changes a lot: the liquid electrolyte disappears and its 'charge carrier' functions are instead performed directly by the separator. The separator in this case is solid, i.e. usually composed of a rigid ceramic or polymer material, which supports the anode and promotes the passage of ions. Looking at the electrodes, the cathode can remain quite similar to that present in a lithium ion battery, while the anode is eliminated, or rather, replaced, by pure metallic lithium, which accumulates directly on the base of the separator during the charging phase without needing the graphite structure present in lithium ions, and passes into the cathode during the discharge phase.



Article from: e-ricarica


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