Better Ways To Extend Life of Solid-State Lithium-Ion Batteries

Better Ways To Extend Life of Solid-State Lithium-Ion Batteries ...

The solid-state battery is a particularly promising technique that can potentially not only deliver twice the amount of energy they need for their dimensions, but also eliminated the danger associated with today''s lithium-ion batteries.

Instabilities at the boundary between the solid electrolyte layer and the two electrodes on the one side can dramatically shorten the life of such batteries. However, some studies have used special coatings to improve the bonding between the layers, but this adds the risk of additional coating steps in the fabrication process. Until today, a team of researchers at the University of Cambridge and the Brookhaven National Laboratory have developed a method to achieve high quality results.

The new approach involves eliminating any carbon dioxide present during a crucial manufacturing step, called sintering, where battery materials are heated to create bonding between the cathode and electrolyte layers, which is made of ceramic compounds. However, the amount of carbon dioxide present is vanishingly small in air, measured in parts per million, and its effects are significant and detrimental. Researchers claim this involves using pure oxygen to create bonds that match the performance of the finest coated surfaces without the added expense of the coating.

In a paper by MIT doctoral student Younggyu Kim, professor of nuclear science and engineering and of materials science and engineering Bilge Yildiz, and Iradikanari Waluyo and Adrian Hunt at Brookhaven National Laboratory, the findings are revealed.

Solid-state batteries have been ideal for several reasons for a long time, according to Yildiz. They are safer and have an increase in energy density, but they have been halted from large-scale commercialization by two factors, according to the company. The lower conductivity of the solid electrolyte, and the interface instability.

According to Yildiz, the conductivity issue has been effectively addressed and good high-conductivity materials have already been demonstrated. However, overcoming the instabilities that arise at the interface has been much more challenging. For the time being, researchers have focused on the manufacture, and particularly the sintering process.

Sintering is required because if ceramic layers are simply pressed onto each other, the contact between them is far from ideal, there are far too many gaps, and the electrical resistance across the interface is significant. Teams experiments showed that at temperatures anywhere above a hundred degrees, detrimental reactions occur that could result in excellent bonding, even when carbon dioxide is present.

Yildiz claims that the performance of the cathode-electrolyte interface made using this method was comparable to those we have seen in literature, but that all were achieved with the added benefit of applying coatings. We are finding that the additional fabrication step is likely to be quite costly.

The increase in energy density that solid-state batteries provide comes from the fact that they allow the use of pure lithium metal as one of the electrodes, which is significantly lighter than the currently used electrodes made of lithium-infused graphite.

The manufacturing process of these batteries is now being investigated, which is how these bonds hold up over the long run during battery cycling. Despite this, the new findings may potentially be applied quickly to battery production. We believe that it can be integrated relatively easily into the fabrication process, and the additional costs, they have calculated, should be negligible.

Large corporations like Toyota are already working on commercializing early versions of solid-state lithium-ion batteries, and these new findings might rapidly assist such companies in improving the value and durability of the technology.

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