All Carbon Dual Ion Batteries

Dual ion batteries based on Na⁺ and PF₆^- received considerable attention due to their high operating voltage and the abundant Na resources. Here, cheap and easily obtained graphite that served as a cathode material for dual ion battery delivered a very high average discharge platform (4.52 V vs Na⁺/Na) by using sodium hexafluorophosphate in propylene carbonate as electrolyte. Moreover, the all-carbon dual ion batteries with graphite as cathode and hard carbon as anode exhibited an ultrahigh discharge voltage of 4.3 V, and a reversible capacity of 62 mAh·g^-1 at 40 mA·g^-1. Phase changes have been investigated in detail through in situ X-ray diffraction and in situ Raman characterizations. The stable structure provides long life cycling performance, and the pseudocapacitance behavior also demonstrates its benefits to the rate capability. Thus, dual ion batteries based on sodium chemistry are very promising to find their applications in future.