A novel sodium-ion capacitor (NIC) was assembled using graphitic mesocarbon microbead anode and activated carbon cathode in diglyme-based electrolyte. Charge/discharge tests indicate that sodium ions can reversibly co-intercalated with diglyme solvent into graphite anode and show good rate performance. The energy densities of the NICs are as high as 93.5 and 86.5 Wh kg−1 at 573 and 2832 W kg−1 (equal to 4 C and 50 C) in the voltage window at 1–4 V, respectively. By optimizing the voltage ranges, the capacity retention of the NIC at 20 C is 98.3% even after 3000 cycles. Such superior electrochemical performance should be attributed to the reversible intercalated/deintercalated reaction of sodium ions and the formation of ternary graphite intercalation compounds in diglyme-based electrolyte. The present work pioneers new realms of hybrid energy storage system with high energy density, high power density and long cycle life.