A naturally occurring red bread mould might be the key to developing rechargeable batteries that are more sustainable than current manganese oxide and lithium-ion batteries, scientists say.
The researchers show for the first time that the fungus Neurospora crassa can transform manganese into a mineral composite with favourable electrochemical properties.
"We have made electrochemically active materials using a fungal manganese biomineralisation process," said Geoffrey Gadd of the University of Dundee in Scotland.
"The electrochemical properties of the carbonised fungal biomass-mineral composite were tested in a supercapacitor and a lithium-ion battery, and it was found to have excellent electrochemical properties," Gadd said.
"This system therefore suggests a novel biotechnological method for the preparation of sustainable electrochemical materials," he said.
Researchers have long studied the ability of fungi to transform metals and minerals in useful and surprising ways. In earlier studies, the researchers showed that fungi could stabilise toxic lead and uranium, for example.
"We had the idea that the decomposition of such biomineralised carbonates into oxides might provide a novel source of metal oxides that have significant electrochemical properties," Gadd said.
There have been many efforts to improve lithium-ion battery or supercapacitor performance using alternative electrode materials such as carbon nanotubes and other manganese oxides.
However, few had considered a role for fungi in the manufacturing process.
The researchers incubated N crassa in media amended with urea and manganese chloride (MnCl2) and found that the long branching fungal filaments (or hyphae) became biomineralised and/or enveloped by minerals in various formations.
After heat treatment, they were left with a mixture of carbonised biomass and manganese oxides.
Further study of those structures show that they have ideal electrochemical properties for use in supercapacitors or lithium-ion batteries.
In comparison to other reported manganese oxides in lithium-ion batteries, the carbonised fungal biomass-mineral composite showed an excellent cycling stability and more than 90 per cent capacity was retained after 200 cycles, Gadd said.
The new study is the first to demonstrate the synthesis of active electrode materials using a fungal biomineralisation process, illustrating the great potential of these fungal processes as a source of useful biomaterials.
The study was published in the journal Current Biology.
