Another Possible Solid State Lithium Electrolyte Material

The search is on for a viable solid state lithium battery electrolyte—this one shows promise because of its high lithium ion diffusion coefficient.

One of the most promising ways to increase lithium ion battery performance and safety is through the use of a solid electrolyte. Present commercial lithium ion batteries use an organic liquid electrolyte that provides good mobility of lithium ions between the anode (negative) and cathode (positive) electrodes. The organic solvent is flammable and thus can be a fire hazard should the battery cell become damaged or if it is over charged.

Examining the crystal structure of LTPS is helping materials researchers understand the mobility of lithium ions in solid electrolytes. (Image source: UCLouvain)

Substituting a ceramic or polymer solid electrolyte for the organic solvent would help make the battery safer and, if lithium metal foil is used to replace the current graphite anode, could increase battery performance and storage capacity by 2-3 times. Lithium metal cannot be used as an anode with liquid electrolytes as spikey dendritic lithium crystals form on the metal surface during charging. These crystals can grow large enough to create a short circuit between the anode and cathode, potentially creating a fire hazard.

Better Mobility

So the search is on for a solid material that should allow safer higher capacity lithium-based batteries. The problem is that lithium ions are less mobile in most solid materials than they are in liquid electrolytes, which limits the battery charging and discharging capabilities. That’s why research at Université catholique de Louvain (UCLouvain) in Belgium into a recently discovered material is interesting. According to a news release, the researchers observed that in LiTi2(PS4)3 or LTPS, they measured the highest lithium diffusion coefficient (a direct measure of lithium mobility) ever measured in a solid.

According to the news release, “This lithium mobility comes directly from the unique crystal structure (i.e., the arrangement of atoms) of LTPS. The understanding of this mechanism opens new perspectives in the field of lithium ion conductors and, beyond LTPS, opens an avenue towards the search for new materials with similar diffusion mechanisms.”

Of course, measuring high lithium ion diffusion rates in a laboratory is a long way from building commercial batteries for use in portable electronics and electric vehicles (EVs). While it is easy to overestimate the importance of such developments, the real value in this type of basic research is an enhanced understanding of the mechanisms and physics involved. With greater understanding will come improved materials, which will eventually result in dramatically better batteries.

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Senior Editor Kevin Clemens has been writing about energy, automotive, and transportation topics for more than 30 years. He has masters degrees in Materials Engineering and Environmental Education and a doctorate degree in Mechanical Engineering, specializing in aerodynamics. He has set several world land speed records on electric motorcycles that he built in his workshop.

 

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