Here I listed some differences quickly summarized between capacitors and batteries (not exhaustive):
- Capacitors store its energy across an interface between an electrode and an electrolyte in a Helmoltz double ions layer; while batteries store energy in a chemical form by intercalation of lithium cations (or Na, K, Mg..) in a "host" structure, usually a layered oxide for the cathode and carbon graphite for the anode.
- Capacitors commonly use highly porous electrode materials (high specific area) made of carbon such as activated carbons, graphite or nanotubes... Cells are symmetrical, applying a voltage to the capacitor at both electrodes generate the double-layer.
- Batteries use different materials for the cathode and the anode, one with a high electrochemical potential, the other with a low potential. Few anode materials are used, carbon graphite, Li4Ti5O12, silicon, carbon-silicon composite... while a variety of cathode compounds can be found, gathered in families: intercalation :layered oxides, olivine, spinels...; and conversion alloys.
-Capacitors have great specific power (W/kg) but low specific energy (Wh/kg), while batteries provide opposite features,
- Capacitors can operate very fast charge/discharge cycles (within few seconds) for a large number of cycles (hundreds of thousands or more) and this for a relatively wide range of temperatures, while a battery takes few minutes to 1 hour at least to be charged and can cycle around 500 to 1000 times for most of the systems within a narrower optimal temperature window,