Fig. 7: Electrochemical energy storage performance of the pre-sodiated hard carbon||P2-NaMNNb coin cells at various temperatures.
From: Niobium-doped layered cathode material for high-power and low-temperature sodium-ion batteries

a The electrochemical curves of the full-cell with various specific current. b The rate performance of the full-cell at 25 °C and −40 °C. c Cycling performance in a rate of 920 mA g−1 at 25 °C and 92 mA g−1 at −40 °C.