Graphene Spacing 'Janus' Could Offer Sodium-Ion Batteries a Tenfold Boost in Capacity

The technology brings the capacity of sodium intercalation in standard graphite from 35 milliampere hours per gram to a whopping 332.
Loukia Papadopoulos

Graphene has been used in many battery components. In June of 2020, a team of researchers from Brown University found a way of using graphene to double the toughness of a ceramic material used to make solid-state lithium-ion batteries. Meanwhile, in April of 2019, a graphene sponge was discovered that could help stabilize lithium-sulfur batteries.

In fact, the potential of graphene in renewable energy systems has been much discussed. But it always seemed that there was some limitation holding the technology back.

Now, researchers at Chalmers University of Technology have conceived of a new concept to fabricate high-performance electrode materials for sodium batteries whose capacity could match today’s lithium-ion batteries based on a novel type of graphene called Janus (named after the Roman god with two faces).

Compared to lithium, which is very expensive and comes with environmental concerns, sodium is an abundantly available low-cost metal that is also eco-friendly. However, currently, sodium-ion batteries have several performance issues.

One of their main issues is graphite, which is used as the anode in today’s lithium-ion batteries. In lithium-ion batteries, the ions intercalate in the graphite, moving in and out of the graphene layers and becoming stored for energy usage.

Sodium ions, however, are too large to be efficiently stored in the graphite structure. This is where the Chamers researchers' invention comes into play. 

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“We have added a molecule spacer on one side of the graphene layer. When the layers are stacked together, the molecule creates larger space between graphene sheets and provides an interaction point, which leads to a significantly higher capacity,” researcher Jinhua Sun at the Department of Industrial and Materials Science at Chalmers and first author of the scientific paper, explained in a statement.

This is great news as the technology brings the capacity of sodium intercalation in standard graphite from 35 milliampere hours per gram (mA h g-1) to a whopping 332 milliampere hours per gram (close to the value for lithium in graphite). The future of sodium-ion batteries is here!

The research is published in Science Advances