It has been known for some time that if you construct a Li-ion battery using anodes made from silicon rather than the more usual carbon, it will result in a cell with a ten-fold increase in charge capacity. The reason silicon is not used is because it is subjected to fairly enormous size fluctuations (up to 400%) which begins after a few charging cycles to destroy the structure of the anode and thus significantly reduce the cell’s usable capacity.
Over the years many optimistic research results claim to have solved the problem of swollen Si electrodes but so far none of the battery designs have made it into production despite the potentially huge increase in capacity on offer.
According to IFE it has developed – (standby, details have yet to be revealed) – a cell that can achieve three to five times the charge capacity of today’s batteries based on ‘common graphite technology’. The technology behind the breakthrough is currently undergoing patent approval.
The Norwegian Research Council supports the research under the FORNY2020 program. The process is currently being tested with international industry partners to test compatibility with industrial manufacturing processes.
The new anode material called SiliconX consists of nanoparticles structured as a matrix of silicon along with other materials. Although these other materials reduce the potential capacity increase compared to pure silicon, they provide sufficient stability and prevent the massive anode volume fluctuations. The resulting compromise still leads to a respectable capacity increase from 3 to 5 times higher when compared with cells using graphite anodes.
The graph shows charge capacity against charge cycles.
- Pure anode silicon batteries (upper black trace)
- SiliconX battery (middle turquoise trace)
- A standard commercial anode material (lower grey trace)