The new energy storage combines two subgroups of battery development: solid-state electrolyte with an anode made entirely of silicon. The result is a highly energy-dense, cheap and durable battery that can be used as a grid storage device in the same way as in electric cars and the electric aircraft that are being developed.
The all-silicon anode is known to be energy-dense, which is ten times the energy density of graphite anodes widely used in commercially available batteries today. However, the practical application of the former has so far been largely limited by their rapidly deteriorating performance when combined with liquid electrolytes. Researchers at the University of California San Diego and LG Energy Solution have worked together to address this problem.
Many see the future of next-generation batteries, and hence higher energy density, in lithium metal anodes, but for the time being these too have problems. For example, they have very limited charging speeds and the charging process itself requires higher temperatures (60 degrees Celsius or more). In the case of the all-silicon anode, there are no such problems: charging is fast, room temperature (or even lower) is sufficient, and the higher energy density is maintained. After 500 charge cycles, the battery tested in the lab retained 80 percent of its original capacity at room temperature, a huge step forward for both silicon anode and solid-state battery development.
One of the serious practical drawbacks of silicon anodes was that they survived few charge cycles without losing their performance. This was mainly due to the interactions between the silicon anode and the liquid electrolytes. But in the current development, all materials other than silicon have been removed from the anode – including carbon and other binders. In addition, the battery uses microsilicon as opposed to the nanosilicon used in the past – and because the former is less processed than the latter, it is cheaper. Finally, the liquid electrolyte was also replaced by a sulphide-based solid electrolyte to eliminate the negative effects described above. The result of the experiments is an extremely stable battery with an anode made of silicon alone, whose performance surprised even the researchers. Another reason is that, since the anode does not contain carbon, there are no side effects with the solid electrolyte that would lead to a permanent loss of capacity.
The final version is therefore cheap, can store a lot of energy and is environmentally friendly. The researchers are continuing development, but in the meantime a start-up they have founded, UNIGRID Battery, has already patented the technology.