Next generation electric vehicles, the development of smart grid solutions and the need for more efficient utilisation of renewable power, demands Li-ion batteries with higher storage capacity. Current Li-ion batteries are limited by the material properties of graphite and cannot fulfill the future capacity need. Replacing graphite with silicon would solve this problem.
Until now, the problem with silicon based Li-ion batteries has been restrictions in how many times the batteries can be charged. In 2015, Elkem made good progress in increasing the numbers of charging cycles. The ground-breaking research is supported by the Research Council of Norway. Elkem has carried out research on developing the optimal silicon material for batteries since 2010. In theory it is possible to increase battery capacity tenfold by using silicon as the anode material. The problem with silicon, however, is that it expands 3-400 per cent when it reacts with lithium during discharge. This can lead to the pulverisation of the anode, meaning that the battery looses capacity.
Silicon and graphite
Elkem has its own divisions of specialists in both carbon and silicon who, together with the Institute for Energy Technology (IFE) and SINTEF in Norway have tried to find mix proportions with silicon that can withstand enough charging cycles to be used in, for example, a car. Binding together microscopic particles of silicon and graphite leaves enough room in the structure for the silicon elements to expand and contract without the substance being pulverised.
In 2015, Elkem Technology concluded a three-year research project and decided to transfer the battery development project to Elkem Silicon Materials. This indicates a possible commercialisation in foreseeable future. During 2015 tests have been done with Si-batteries that have double storage capacity compared with ordinary batteries. Results show that a battery with a silicon/graphite anode could do more than 1000 charge cycles. This is, however, still low for most electrical vehicles.
To improve these results, the two new research projects "Silicon anodes for Li-ion batteries – optimised binder, electrolyte and cathode" and "Industrial scale silicon - carbon composites adapted to battery grade anode material" have been launched. The goal is full industrial use of silicon as anode material.
Elkem currently produces speciality silicon, Silgrain® e-Si, at the plant in Bremanger, Norway. Elkem’s unique production process gives Silgrain® e-Si a considerably lower environmental footprint than comparable silicon materials, a pH that limits hydrogen gas development during processing of slurries and high consistency in size and chemical composition. Institutes and Li-ion battery producers use Silgrain® e-Si in battery Li-ion batteries. Silgrain® e-Si was developed in collaboration with AISTKansai, a Japanese research centre.