A layer-structured Na2CoP2O7 pyrophosphate cathode for sodium-ion batteries

We introduce Na2CoP2O7 pyrophosphate as a new potential cathode for sodium-ion batteries. Based on a layered structure, it offers a two-dimensional Na-diffusion pathway delivering a reversible capacity close to 80 mA h g(-1) involving Co3+/Co2+ redox activity with an average potential of 3 V.