Carbon Cryogels and Carbon Fiber Paper as Approaches for Silicon Anodes for Li-ion Batteries
23 June 2010
A team at NASA Glenn Research Center will present a paper at the upcoming 218thECS meeting (10-15 October 2010) on an investigation of three different approaches to incorporating silicon into anode materials for higher capacity lithium-ion batteries: two based on silicon-carbon composite materials (carbon cryogels) and one using carbon fiber paper as an active material current collector/support material.
The two silicon-carbon composite materials are formed via the dispersion of silicon in a resorcinol-formaldehyde (RF) gel followed by pyrolysis and possess either microsphere or nanofoam morphologies.
The premise behind the RF gel silicon composite is that the gel will form a flexible, porous, carbon matrix around the silicon particles capable of absorbing their large volume expansion upon lithiation, thereby maintaining electrical contact between the silicon particles and the current collector and addressing the capacity fade issues faced by silicon anodes with cycling. The carbon matrix will also prevent direct electrolyte contact with the silicon.
In the case of the nanofoam material, Woodworth et al. say, the carbon paper and matrix surrounding the silicon can act as the current collector, thereby significantly reducing weight by eliminating the need for a copper current collector.
The team reports stable reversible capacities above 400 mAh g-1 for the bulk material and above 1000 mAh -1 of Si.
In the third approach, carbon paper is impregnated with a slurry composed of nano-silicon powder, a binder, and carbon black. The use of carbon paper significantly reduces weight by eliminating the need for a copper current collector. Additionally, this approach implements electrode fabrication methods commonly utilized in the lithium battery industry.
Resources
James F. Woodworth, Richard Baldwin and William R. Bennett (2010) Silicon Composite Anode Materials for Lithium Ion Batteries Based on Carbon Cryogels and Carbon Paper (ECS 218)
Another promising approach to improve future lithium batteries performance while potentially reducing cost. More improvement will certainly come from worldwide R & D.
Meanwhile five lithium (rock) mines in Northern Canada will join forces to build a shared concentrator. Their potential yearly production could be enough for 1+ M EVs @ 24 Kwh each by 2015. Many more lithium mines could begin operation by 2020. The world will not be short of lithium.
Posted by: HarveyD | 23 June 2010 at 08:22 AM
Initially there will be enough lithium, it is balancing supply with demand for batteries. You would not build a large automated battery factory if you did not have lots of customers that you could count on for continued business.
The whole push for lithium chemistries is in part due to the success of HEVs. Perhaps the utilities with smart grid batteries will provide another large customer base to spur even more progress. One thing leads to another, but you have to have some assurances to make it all go round.
Posted by: SJC | 23 June 2010 at 10:03 AM