A TiSe2 -Graphite Dual Ion Battery: Fast Na-Ion Insertion and Excellent Stability.

The sodium dual ion battery (Na-DIB) technology is proposed as highly promising alternative over lithium-ion batteries for the stationary electrochemical energy-storage devices. However, the sluggish reaction kinetics of anode materials seriously impedes their practical implementation. Herein, a Na-DIB based on TiSe2 -graphite is reported. The high diffusion coefficient of Na-ions (3.21×10-11 -1.20×10-9  cm2  s-1 ) and the very low Na-ion diffusion barrier (0.50 eV) lead to very fast electrode kinetics, alike in conventional surface capacitive storage systems. In-situ investigations reveal that the fast Na-ion diffusion involves four insertion stage compositions. A prototype cell shows a reversible capacity of 81.8 mAh g-1 at current density of 100 mA g-1 , excellent stability with 83.52 % capacity retention over 200 cycles and excellent rate performance, suggesting its potential for next-generation large scale high-performance stationary energy storage systems.