It exploits the high surface area of gold nano-wires coated with manganese dioxide, into which lithium ions are added and removed.

The cells are symmetrical, with identical nano-wires attached to both electrodes, separated by a void filled with an electrolyte made from propylene carbonate and lithium perchlorate.

What makes the diffeence between a long life and a very long life is the addition The difference between a long life an a very long life is a gelling agent (20% of PMMA – polymethylmethacrylate – Perspex).

Without gel stabilisation, life is shorter. “These things typically die in dramatic fashion after 5,000 or 6,000 or 7,000 cycles at most,” said researcher Reginald Penner.

With the gel stabilisation, “the coated electrode holds its shape much better, making it a more reliable option”, said project leader Mya Le Thai. “This research proves that a nanowire-based battery electrode can have a long lifetime and that we can make these kinds of batteries a reality.”

The theory is that the gel physically constrains plasticises the manganese oxide, giving it flexibility which prevents cracking. Without it, the oxide both migrates and falls off.

There is no reduction in cell capacity, although with the gelling agent the cell takes weeks to reach full capacity – something that may be due to the slow rate at ewhich the gel penetrates the porous oxide, said the scientists.

The work is published in ACS Energy Letters – ‘100k cycles and beyond: extraordinary cycle stability for MnO2 nanowires imparted by a gel electrolyte‘.

There is a video to watch here.

The team points out that life in hundreds of thousands of cycles has previously been demonstrated in a loosely similar arrangement with Mn2O3 films (and aqueous Na2SO4 electrolyte) rather than coatings on nanowires – (Anomalous pseudocapacitive behavior of a nanostructured, mixed-valent manganese oxide film for electrical energy storage – Nano letters 2012).