Why not combine a lead acid or Li-ion with a cheaper ultracapacitor.

There is a new one comong on the market which has the promise of solving the problem. It has 10-20 times the power and energy density as the ultracaps presently on the market. Here is a paper I found on the internet. It is called Reticle Carbon.
A New Material for Ultracapacitors
March 11, 2009 |
The popular and news making EEStor has a competitor coming. EEStor, now famed for their secrecy about what goes in their capacitor, leaves lots of room for speculation. Of note is they have gained more credibility over the years and seem closer to delivering product.

The ultracapacitor field is based on simple, or as simple as possible, electron storage. For that to happen the electrons need to ‘park’ on something that will take them on and let them go easily. Conductive materials are obvious choices. Constructing ultracapacitors seems simple but entails considerable materials and assembly sophistication.

Dr. Carl C. Nesbitt the CEO and Chief Technology Officer at Reticle Inc. Los Altos, California is following his experience with the carbon his company uses for water treatment and other filtration processes into ultracapacitors. Reticle’s other carbon products are likely supporting the whole of the research effort and Dr. Nesbitt has made quite substantial and impressive progress. From his discussion on ultracapacitors.org we’ll have an overview look for today.

Dr. Nesbitt has developed a unique electrode material he’s named ‘Reticle Carbon’ that’s ideally suited for electric double-layer ultracapacitors. Reticle Carbon is simple to manufacture yet has low electrical resistance (low ohms) with high surface areas (1,250-1,750 m2/g), and the highest reported specific capacitance (200-310 F/g). Activated carbon is used to make Reticle Carbon by consolidating granular activated carbon that has been selected for its properties with no binders, fillers or adhesives. The manufacturing process is single-stage, but flexible enough so that the company can tailor the properties of the material for ultracapacitors.

Dr. Nesbitt does a very good explaining some of the important attribute of capacitors, a little more than a paragraph that will refresh and inform. Then he explains the carbon sources and processes used to build the particles that store or ‘park’ electrons. The discussion makes clear the importance of surface area to make capacitors with very high storage volumes.

Reticle Bond Points. Click image for more.

Then the issue becomes getting electrons in and out. For this to happen at low voltages the materials whether carbon or not, need to be in contact with each other and with the electrodes that carry electrons in and out. What may be Reticle’s breakthrough is Dr. Nesbitt asserts he has a technology to form the carbon into a fully connected ‘solid’ – free of binder chemicals, adhesives or highly pressurized constructions. As you can imagine adding substances would form current barriers and high compression would crush out the total surface area.

Reticle uses temperature and pressure to form small bonds among all of the particles. The process can be tailored for unique properties, such as macroporosity ranging from 10-40%, good electrical resistance and thermal conductivity measured as low as 0.1 W/m.K. However, the most unique property of the material is the demonstrated high surface areas, ranging from 1,250 to over 1,750 m2/g, which is a function of the commercial grade carbon selected as the precursor. Compared with other activated carbon materials, this is an exceptionally high surface area range with high conductivity.

Loose Distribution vs Reticle Consolidation. Click image for more.

Connecting all of the particles is significant, particles must touch to ensure that all of the charge is distributed across all of the surface area – any particles not in direct, constant contact will not charge, wasting volume and materials. In other ultracapacitor designs as the material gets thicker the missed connections accumulate limiting the potential dimensions. Reticle is claiming their build process is fully linking the particles removing the dimensional limits.

That leads to the process making a variable amount of charge as design criteria demand. The more the Reticle process consolidates the carbon more total charge with higher conductivity. Lighter consolidation would increase the capacity at higher ohms. One might envision that the voltage and weight considerations in a design would drive the consolidation selections.

Reticle Late Prototype. Click image for more.

Dr. Nesbitt acknowledges that Reticle is looking for capital to begin commercial production. The company has simple prototypes built with very low cost materials in simple constructions. The first prototype was built using 0.4 grams of the lightly consolidated carbon yielding 53F/g of specific capacitance. Nesbitt expects, fairly it seems, that using Reticle carbon will obtain higher capacities as the improved carbon and consolidation is incorporated into test units. It seems likely that test units might be available.

This is the point at which the remaining issue, that of the electrolytes, comes up. Nesbitt acknowledges that the commercially available electrolytes are limitations at the capacities of the Reticle prototypes. At such intense densities a higher level of ionic strength is needed, a market demand that isn’t being answered as other than Reticle – no customers exist.

Dr. Nesbitt’s discussion closes with an analysis of the Reticle position today versus the two main shipping competitors. As the discussion flows one becomes aware that the company is already quite competitive and has major advantages to offer as the electrolyte issue resolves and experience is gained adding more innovation to the basic science.

Reticle carbon offers new and unique properties in basic matters such as raw material availability, processing costs, gross capacity and low investment thresholds. As demand grows and should adequate capital appear Reticle’s new form of consolidated activated carbon offers a good path the huge electrical storage in the expanding field of ultracapacitors.

What is interesting beyond the technology is the attention given to the physical volumes and weights of the Reticle ultracapacitors. One main attraction of capacitors over batteries in portable and transport applications is that capacitors are lighter and weight matters a great deal. It’s a coincidental pity that Dr. Nesbitt and his technology are coming to maturity just as two of the U.S. auto manufacturers are flirting with bankruptcy. This technology just might be better than my personal goal that charging will need to get below 10 minutes per 100 miles of range.

Congratulations Dr. Nesbitt. I hope this post will push something or someone useful your way.