Fig. 2: Na+ storage performances within 0.1–3.0 V.

a Cycling performance and c rate capability of Na||HESSe, Na||LESSe and Na||CuS cells with filled and unfilled circles denoting charge and discharge processes, respectively. b Charge/discharge profiles of Na||HESSe cell at 0.4 A g−1. Cycling performance of Na||HESSe cell at d 6.0 A g−1 and e 30 A g−1. f Charge/discharge profile of Na||HESSe cell at 30 A g−1. g Comparison of Na||HESSe cell with other reported transition metal chalcogenides positive electrodes; detailed electrochemical data are provided in Supplementary Table 7.