Magnetically aligned graphite electrodes for high-rate performance Li-ion batteries

As lithium-ion batteries become ubiquitous, the energy storage market is striving for better performance, longer lifetime and better safety of the devices. This race for performance is often focused on the search for new materials, whereas less effort has been dedicated to the electrode engineering. Enhancing the power density by increasing the amount of active material remains impractical since it impinges the transport of ions across the electrode during the charging and discharging processes. Here, we show that the electrochemical performance of a battery containing a thick (about 200 μm), highly loaded (about 10 mg cm−2) graphite electrode can be remarkably enhanced by fabricating anodes with an out-of-plane aligned architecture using a low external magnetic field. The lower tortuosity resulting from such a simple and scalable magnetic alignment approach leads to a specific charge up to three times higher than that of non-architectured electrodes at a rate of 1C. A common problem for thick electrodes in lithium-ion batteries is slow ionic transport. Here, the authors present a particle-alignment method that uses a low magnetic field and show that the lithium diffusion path is improved for an aligned thick graphite electrode, leading to a better rate capability.