Researchers at Stanford University in the United States and Hanyang University in Korea, have shown that replacing the conventional graphite electrodes in lithium-ion batteries with silicon nanotubes can produce a battery capable of holding ten times more charge. Working in cooperation with battery maker LG Chem, the laboratories developed a silicon anode which can store more energy because it absorbs higher levels of lithium when the battery is charged. The researchers say that, when the new silicon anode can be matched to a cathode of similar storage capacity, the resulting battery should represent an improvement on today’s technology of between 6x and 10x in terms of energy delivery.
The ability of a silicon anode to absorb much more Lithium than a carbon-based anode has been known for some time, but when most forms of silicon are used, rapid volume changes cause cracking and degradation in the brittle substance over only a few charge/discharge cycles.
It seems that the nanotube shape provides more surface area with which the ions can interact, as well as more space between molecules, both of which act to reduce the mechanical strain on the material when the battery is charged and discharged. So far the nanotube anode has been shown not to degrade over 200 cycles, which is a tremendous improvement, but of course it will need to be proven over tens of thousands of cycles before being considered vehicle ready.
Because the process of producing silicon nanotubes is well understood and the methodology is already being used commercially, the researchers believe that batteries incorporating silicon electrodes could be on the market in as little as three years. The team is currently working on developing new cathode materials in collaboration with LG Chem.