|Nexeon silicon anode materials. Left: 1st generation, up to 1,000 mAh g-1. Right: 2nd generation, up to 3,600 mAh g-1. Source: Nexeon. Click to enlarge.|
According to a report in EETimes, UK start-up Nexeon Limited, a spin-off from Imperial College London based on work done by Professor Mino Green, Emeritus Professor at the Department of Electrical Engineering (earlier post), is getting ready to license its silicon anode technology for Li-ion batteries, and is in talks with battery makers.
Nexeon has developed and patented a novel way of structuring silicon so that it delivers extended cycle life and significantly increases anode charge capacity—almost ten times the gravimetric capacity per gram (mAh g-1) compared to carbon anodes. Used in combination with a standard cathode, this can increase cell capacity by 30-40%, Nexeon says.
Silicon is conceptually an attractive anode material for lithium-ion batteries because of its high theoretical charge capacity (4,200 mAh g-1—more than 10 times that of graphite anodes and much larger than various nitride and oxide materials) and low discharge potential. However, silicon anodes are problematic because the material’s volume changes by up to 400% upon the insertion and extraction of lithium ions during charge/discharge cycles. This results in pulverization and capacity fading.
Nexeon says that its patented silicon structures overcome the poor cycle life problems by mitigating the volume expansion issue. These structured silicon anode materials deliver extended cycle life without degradation of capacity.
Nexeon is developing a range of materials with different morphologies and capacities. It says its first commercially available material is capable of capacities up to 1,000 mAh g-1. (As an application example, 2.6g of Nexeon’s first generation structured silicon can replace around 10g of graphite anode material in a commercial 2600 mAh 18650 cell.) Nexeon says it is working on a second-generation material with a different morphology optimized for higher capacities of up to 3,600 mAh
The graphite currently used it cells can be replaced with Nexeon materials and used in combination with conventional polymer binders and current collectors as part of the standard battery manufacturing process, the company says, offering a “drop-in” solution to higher capacities.
The company has a fully automated and instrumented pilot plant in full operation, capable of producing more than 1 kg of material a day (enough material for approximately 500 x 18650 cells). Further proprietary equipment has been designed and is now in the final stages of being tested