Introduction to Neocarbonix: Binderless Electrodes for Lithium-Ion Batteries

Abstract

Energy storage electrodes are often limited in their electrochemical stability and electrical performance by polymer binders used in the active material layer. Binders are also used to adhere the active material to the current collector. Binders are usually polymeric resins used in electrodes to mechanically hold active material powders together. Active materials may be graphite, silicon-carbon, silicon oxides for anodes, and lithium metal oxides for cathodes in the case of lithium-ion batteries (LIBs). They can also be high surface area activated carbons, in the case of EDLCs. The binders are a passive component in energy storage electrodes and they carry limitations in terms of electrical conductivity, thermal stability and chemical stability.Capacity and C-rate capabilities in LIBs and ESR in EDLCs suffer because electrically insulating inactive binder material takes up space within the electrode material. Meanwhile lifetime at temperature and voltage can suffer as the binder material interacts with the internal electrochemical system of the energy storage device. Additionally, thermal stability of the electrode can be limited both by the electrochemical activity of the binder material as well as phase transitions of the binder material. Performance of energy storage systems using conventional electrodes in particularly high power applications may be limited by the thermal stability of the binder as well. Internal heat dissipation in those applications can be a serious concern when combined with ambient temperatures, especially in space-constrained environments or in applications where thermal management is at a premium. Energy density is also limited by the thickness of active materials that a standard coating process with binder-containing slurry can yield. Finally, cost of electrode production is dramatically impacted by the slurry drying step, as strong solvents with high boiling point (e.g. NMP) must be used to dissolve polymer binders, and are difficult to evaporate.Nanoramic has developed an alternate solution - Neocarbonix - an electrode platform technology that effectively replaces polymer binders and primers. Results have been demonstrated for both LIB cathodes and EDLC electrodes. Nanoramic's Neocarbonix electrodes have significantly lower ESR, better C-rate capabilities, greater active material thickness for improved energy density, while also retaining or improving specific capacity. Lifetime at high temperature is also significantly improved, because of the increased thermal and chemical stability of the electrodes.Electrode production cost is also dramatically reduced, as the Neocarbonix process is solvent-agnostic. The solvent can be selected to speed up the drying process during coating, which dramatically improves the production throughput.