Nanotune Technologies’ CEO Kuang Tsei Huang has demonstrated supercapacitors with 35 Wh/kg, saying that 500 Wh/kg may be achievable, 2-4 times the energy density of the best Li-ion batteries, IDTech notes. Yunasko and others have demonstrated 35 Wh/kg, with the intermediate supercabatteries, matching lead-acid and NiCd batteries. Maxwell Technologies expects tripling current energy density with pure supercapacitors. Graphene supercapacitor developers target 200 Wh/kg.

Supercapacitors need not match lithium-ion battery energy density to replace much of that battery market. They have replaced maybe one percent of that market already with only one hundredth of the energy density because they last longer than the bus for example that they are in. They are safer and have ten times the power density. Even across batteries they mean less battery is needed.

They have replaced Li-ion batteries in most Chinese buses, despite greater up-front price. Supercapacitor sales are under 3% of lithium-ion battery sales today, partly replacing them and partly doing things batteries can never do.

Supercapacitor sales will be over 10% of Li-ion sales in ten years as they grab more Li-ion business despite such batteries improving by a factor of two in energy density. For that, production supercapacitors or supercabatteries (notably lithium-ion capacitors) must reach around 40 Wh/kg with all other parameters acceptable, possibly even conceding some power density and life but being greener. If that happens, few will dispute that in the next decade at around 100 Wh/kg with acceptable other parameters, supercapacitors or supercabatteries could grab 50% of the lithium-ion market reaching tens of billions of dollars in yearly sales.

—Dr. Peter Harrop, Chairman of IDTechEx